diff --git a/tcms/static/js/utils.js b/tcms/static/js/utils.js
index 8e912edad7..27c5b66891 100644
--- a/tcms/static/js/utils.js
+++ b/tcms/static/js/utils.js
@@ -560,6 +560,186 @@ export function showOrHideMultipleRows (rootSelector, rows) {
     }
 }
 
+/*
+    Reusable duplicate-check logic for "new" forms.
+
+    config = {
+        rpcMethod:      'TestCase.filter',     // JSON-RPC method
+        fieldName:      'summary',             // model field name
+        inputSelector:  '#id_summary',         // input element
+        groupSelector:  '#summary-group',      // form-group with data-trans-* attrs
+        warningSelector:'#duplicate-summary-warning',
+        autocompleteSelector: '#summary-autocomplete',
+        modalSelector:  '#duplicate-tc-modal',
+        prefix:         'TC',                  // display prefix, e.g. TC, TR, TP
+        detailUrlBase:  '/case/',              // URL path for detail view
+        modalRows:      function(g, item) {},  // returns array of [label, value]
+        descriptionField: 'text'               // field name for markdown description, or null
+    }
+*/
+export function initDuplicateCheck (config) {
+    const duplicateWarning = $(config.warningSelector)
+    if (!duplicateWarning.length) {
+        return
+    }
+
+    const group = $(config.groupSelector)
+    const input = $(config.inputSelector)
+    const autocomplete = $(config.autocompleteSelector)
+    const modal = $(config.modalSelector)
+    const maxItems = 10
+    let debounceTimer = null
+    let duplicateMatches = []
+
+    function showModal (item) {
+        const g = group.data.bind(group)
+        $('#duplicate-modal-title').text(
+            g('trans-duplicate-modal-title') + ' - ' + config.prefix + '-' + item.id
+        )
+
+        $('#duplicate-modal-view-btn').attr('href', config.detailUrlBase + item.id + '/')
+        $('#duplicate-modal-view-label').text(
+            g('trans-duplicate-modal-view') + ' ' + config.prefix + '-' + item.id
+        )
+
+        const body = $('#duplicate-modal-body')
+        body.empty()
+
+        const table = $('<table>', { class: 'table table-striped table-condensed' })
+        const rows = config.modalRows(g, item)
+        rows.forEach(function (row) {
+            $('<tr>')
+                .append($('<th>', { text: row[0], css: { width: '150px' } }))
+                .append($('<td>', { text: row[1] || '' }))
+                .appendTo(table)
+        })
+
+        if (config.descriptionField) {
+            const descriptionContainer = $('<div>', {
+                css: {
+                    'max-height': '300px',
+                    'overflow-y': 'auto',
+                    'background-color': '#f5f5f5',
+                    padding: '10px',
+                    'border-radius': '4px'
+                }
+            })
+            const descriptionRow = $('<tr>')
+                .append($('<th>', { text: g('trans-duplicate-modal-text'), css: { width: '150px', 'vertical-align': 'top' } }))
+                .append($('<td>').append(descriptionContainer))
+            table.append(descriptionRow)
+            body.append(table)
+
+            const descValue = item[config.descriptionField]
+            if (descValue) {
+                markdown2HTML(descValue, descriptionContainer[0])
+            } else {
+                descriptionContainer.text('-')
+            }
+        } else {
+            body.append(table)
+        }
+
+        modal.modal('show')
+    }
+
+    function updateWarning () {
+        if (duplicateMatches.length > 0) {
+            duplicateWarning.html(
+                '<span class="fa fa-exclamation-triangle"></span> ' +
+                group.data('trans-duplicate-blocked')
+            ).removeClass('hidden')
+        } else {
+            duplicateWarning.addClass('hidden').empty()
+        }
+    }
+
+    const fieldContains = config.fieldName + '__icontains'
+    const fieldIexact = config.fieldName + '__iexact'
+
+    input.on('input', function () {
+        const value = $(this).val().trim()
+        clearTimeout(debounceTimer)
+
+        if (value.length < 3) {
+            duplicateWarning.addClass('hidden').empty()
+            autocomplete.hide().empty()
+            duplicateMatches = []
+            return
+        }
+
+        const filterParam = {}
+        filterParam[fieldContains] = value
+
+        debounceTimer = setTimeout(function () {
+            jsonRPC(config.rpcMethod, filterParam, function (data) {
+                duplicateMatches = data.filter(function (item) {
+                    return item[config.fieldName].toLowerCase() === value.toLowerCase()
+                })
+                updateWarning()
+
+                autocomplete.empty()
+                if (data.length > 0) {
+                    data.slice(0, maxItems).forEach(function (item) {
+                        $('<a>', {
+                            href: '#',
+                            class: 'list-group-item',
+                            text: config.prefix + '-' + item.id + ': ' + item[config.fieldName]
+                        }).on('click', function (e) {
+                            e.preventDefault()
+                            autocomplete.hide()
+                            showModal(item)
+                        }).appendTo(autocomplete)
+                    })
+                    if (data.length > maxItems) {
+                        $('<span>', {
+                            class: 'list-group-item disabled',
+                            text: '... and ' + (data.length - maxItems) + ' more'
+                        }).appendTo(autocomplete)
+                    }
+                    autocomplete.show()
+                } else {
+                    autocomplete.hide()
+                }
+            })
+        }, 500)
+    })
+
+    $(document).on('click', function (e) {
+        if (!$(e.target).closest(config.inputSelector + ', ' + config.autocompleteSelector).length) {
+            autocomplete.hide()
+        }
+    })
+
+    input.on('focus', function () {
+        if (autocomplete.children().length > 0) {
+            autocomplete.show()
+        }
+    })
+
+    duplicateWarning.closest('form').on('submit', function (e) {
+        const currentValue = input.val().trim()
+        if (currentValue.length < 1) {
+            return
+        }
+
+        const exactParam = {}
+        exactParam[fieldIexact] = currentValue
+
+        duplicateMatches = []
+        jsonRPC(config.rpcMethod, exactParam, function (data) {
+            duplicateMatches = data
+        }, true)
+
+        if (duplicateMatches.length > 0) {
+            e.preventDefault()
+            updateWarning()
+            showModal(duplicateMatches[0])
+            return false
+        }
+    })
+}
+
 export function discoverNestedTestPlans (inputData, callbackF) {
     const prefix = '&nbsp;&nbsp;&nbsp;&nbsp;'
     const result = []
diff --git a/tcms/templates/include/duplicate_check_modal.html b/tcms/templates/include/duplicate_check_modal.html
new file mode 100644
index 0000000000..58a35b67b2
--- /dev/null
+++ b/tcms/templates/include/duplicate_check_modal.html
@@ -0,0 +1,22 @@
+{% load i18n %}
+<div class="modal fade" id="duplicate-modal" tabindex="-1" role="dialog" aria-labelledby="duplicate-modal-title" aria-hidden="true">
+  <div class="modal-dialog modal-lg">
+    <div class="modal-content">
+      <div class="modal-header">
+        <button type="button" class="close" data-dismiss="modal" aria-hidden="true" aria-label="Close">
+          <span class="pficon pficon-close"></span>
+        </button>
+        <a id="duplicate-modal-view-btn" href="#" target="_blank" class="btn btn-default btn-sm pull-right" style="margin-right: 10px;">
+          <span class="fa fa-external-link"></span> <span id="duplicate-modal-view-label"></span>
+        </a>
+        <h4 class="modal-title" id="duplicate-modal-title"></h4>
+      </div>
+      <div class="modal-body">
+        <div id="duplicate-modal-body"></div>
+      </div>
+      <div class="modal-footer">
+        <button type="button" class="btn btn-default" data-dismiss="modal">{% trans "Close" %}</button>
+      </div>
+    </div>
+  </div>
+</div>
diff --git a/tcms/testcases/static/testcases/js/mutable.js b/tcms/testcases/static/testcases/js/mutable.js
index c37d9c9e32..afc5c33139 100644
--- a/tcms/testcases/static/testcases/js/mutable.js
+++ b/tcms/testcases/static/testcases/js/mutable.js
@@ -1,4 +1,4 @@
-import { updateCategorySelectFromProduct } from '../../../../static/js/utils'
+import { initDuplicateCheck, updateCategorySelectFromProduct } from '../../../../static/js/utils'
 
 export function pageTestcasesMutableReadyHandler () {
     $('#id_template').change(function () {
@@ -51,6 +51,28 @@ export function pageTestcasesMutableReadyHandler () {
         showMinutes: true,
         showSeconds: true
     })
+
+    initDuplicateCheck({
+        rpcMethod: 'TestCase.filter',
+        fieldName: 'summary',
+        inputSelector: '#id_summary',
+        groupSelector: '#summary-group',
+        warningSelector: '#duplicate-summary-warning',
+        autocompleteSelector: '#summary-autocomplete',
+        modalSelector: '#duplicate-modal',
+        prefix: 'TC',
+        detailUrlBase: '/case/',
+        descriptionField: 'text',
+        modalRows: function (g, tc) {
+            return [
+                [g('trans-duplicate-modal-summary'), tc.summary],
+                [g('trans-duplicate-modal-status'), tc.case_status__name],
+                [g('trans-duplicate-modal-category'), tc.category__name],
+                [g('trans-duplicate-modal-priority'), tc.priority__value],
+                [g('trans-duplicate-modal-author'), tc.author__username]
+            ]
+        }
+    })
 }
 
 function populateProductCategory () {
diff --git a/tcms/testcases/templates/testcases/mutable.html b/tcms/testcases/templates/testcases/mutable.html
index 8da89e7a9b..70f49cf1e4 100644
--- a/tcms/testcases/templates/testcases/mutable.html
+++ b/tcms/testcases/templates/testcases/mutable.html
@@ -20,18 +20,38 @@
         <form class="form-horizontal" action="{% if object %}{% url 'testcases-edit' object.pk %}{% else %}{% url 'testcases-new' %}{% endif %}" method="post">
             {% csrf_token %}
             <input type="hidden" name="author" value="{{ form.author.value }}">
-            <div class="form-group">
+            <div class="form-group" id="summary-group"
+                data-trans-duplicate-blocked="{% trans 'A test case with this exact summary already exists. Duplicates are not allowed.' %}"
+                data-trans-duplicate-modal-title="{% trans 'Duplicate test case found' %}"
+                data-trans-duplicate-modal-summary="{% trans 'Summary' %}"
+                data-trans-duplicate-modal-author="{% trans 'Author' %}"
+                data-trans-duplicate-modal-status="{% trans 'Status' %}"
+                data-trans-duplicate-modal-category="{% trans 'Category' %}"
+                data-trans-duplicate-modal-priority="{% trans 'Priority' %}"
+                data-trans-duplicate-modal-text="{% trans 'Description' %}"
+                data-trans-duplicate-modal-view="{% trans 'View existing test case' %}">
                 <label class="col-md-1 col-lg-1" for="id_summary">{% trans "Summary" %}</label>
                 <div class="col-md-11 col-lg-11 {% if form.summary.errors %}has-error{% endif %}">
-                    <input type="text" id="id_summary" name="summary" value="{{ form.summary.value|default:'' }}" class="form-control" required>
+                    <input type="text" id="id_summary" name="summary" value="{{ form.summary.value|default:'' }}" class="form-control" required autocomplete="off">
+                    {% if not object %}
+                    <div id="summary-autocomplete" class="list-group" style="display: none; max-height: 200px; overflow-y: auto; margin-bottom: 0; background-color: #f5f5f5; border: 1px solid #b7b7b7;"></div>
+                    {% endif %}
                     {% if test_plan %}
                         <p class="help-block"><a href="{% url 'test_plan_url' test_plan.pk %}">TP-{{ test_plan.pk }}: {{ test_plan.name }}</a></p>
                         <input type="hidden" name="from_plan" value="{{ test_plan.pk }}">
                     {% endif %}
                     {{ form.summary.errors }}
+                    {% if not object %}
+                    <div id="duplicate-summary-warning" class="help-block hidden kiwi-color-warning">
+                    </div>
+                    {% endif %}
                 </div>
             </div>
 
+            {% if not object %}
+            {% include "include/duplicate_check_modal.html" %}
+            {% endif %}
+
             <div class="form-group">
                 <label class="col-md-1 col-lg-1" for="id_default_tester">{% trans "Default tester" %}</label>
                 <div class="col-md-3 col-lg-3 {% if form.default_tester.errors %}has-error{% endif %}">
diff --git a/tcms/testplans/static/testplans/js/mutable.js b/tcms/testplans/static/testplans/js/mutable.js
index 7ede72fd13..2b396c9b9d 100644
--- a/tcms/testplans/static/testplans/js/mutable.js
+++ b/tcms/testplans/static/testplans/js/mutable.js
@@ -1,5 +1,5 @@
 import { testPlanAutoComplete } from '../../../../static/js/jsonrpc'
-import { populateVersion } from '../../../../static/js/utils'
+import { initDuplicateCheck, populateVersion } from '../../../../static/js/utils'
 
 const planCache = {}
 
@@ -50,4 +50,26 @@ export function pageTestplansMutableReadyHandler () {
 
     // override the default inline-block style
     $('span.twitter-typeahead').css('display', 'block')
+
+    initDuplicateCheck({
+        rpcMethod: 'TestPlan.filter',
+        fieldName: 'name',
+        inputSelector: '#id_name',
+        groupSelector: '#name-group',
+        warningSelector: '#duplicate-name-warning',
+        autocompleteSelector: '#name-autocomplete',
+        modalSelector: '#duplicate-modal',
+        prefix: 'TP',
+        detailUrlBase: '/plan/',
+        descriptionField: 'text',
+        modalRows: function (g, tp) {
+            return [
+                [g('trans-duplicate-modal-name'), tp.name],
+                [g('trans-duplicate-modal-product'), tp.product__name],
+                [g('trans-duplicate-modal-version'), tp.product_version__value],
+                [g('trans-duplicate-modal-type'), tp.type__name],
+                [g('trans-duplicate-modal-author'), tp.author__username]
+            ]
+        }
+    })
 }
diff --git a/tcms/testplans/templates/testplans/mutable.html b/tcms/testplans/templates/testplans/mutable.html
index 34b8d242a6..36521f218a 100644
--- a/tcms/testplans/templates/testplans/mutable.html
+++ b/tcms/testplans/templates/testplans/mutable.html
@@ -20,14 +20,34 @@
         <form class="form-horizontal" action="{% if object %}{% url 'plan-edit' object.pk %}{% else %}{% url 'plans-new' %}{% endif %}" method="post">
             {% csrf_token %}
             <input type="hidden" name="author" value="{{ form.author.value }}">
-            <div class="form-group">
+            <div class="form-group" id="name-group"
+                data-trans-duplicate-blocked="{% trans 'A test plan with this exact name already exists. Duplicates are not allowed.' %}"
+                data-trans-duplicate-modal-title="{% trans 'Duplicate test plan found' %}"
+                data-trans-duplicate-modal-name="{% trans 'Name' %}"
+                data-trans-duplicate-modal-product="{% trans 'Product' %}"
+                data-trans-duplicate-modal-version="{% trans 'Version' %}"
+                data-trans-duplicate-modal-type="{% trans 'Type' %}"
+                data-trans-duplicate-modal-author="{% trans 'Author' %}"
+                data-trans-duplicate-modal-text="{% trans 'Description' %}"
+                data-trans-duplicate-modal-view="{% trans 'View existing test plan' %}">
                 <label class="col-md-1 col-lg-1" for="id_name">{% trans "Name" %}</label>
                 <div class="col-md-11 col-lg-11 {% if form.name.errors %}has-error{% endif %}">
-                    <input type="text" id="id_name" name="name" value="{{ form.name.value|default:'' }}" class="form-control" required>
-                {{ form.name.errors }}
+                    <input type="text" id="id_name" name="name" value="{{ form.name.value|default:'' }}" class="form-control" required autocomplete="off">
+                    {% if not object %}
+                    <div id="name-autocomplete" class="list-group" style="display: none; max-height: 200px; overflow-y: auto; margin-bottom: 0; background-color: #f5f5f5; border: 1px solid #b7b7b7;"></div>
+                    {% endif %}
+                    {{ form.name.errors }}
+                    {% if not object %}
+                    <div id="duplicate-name-warning" class="help-block hidden kiwi-color-warning">
+                    </div>
+                    {% endif %}
                 </div>
             </div>
 
+            {% if not object %}
+            {% include "include/duplicate_check_modal.html" %}
+            {% endif %}
+
             <div class="form-group">
                 <div class="col-md-1 col-lg-1">
                     <label for="id_product">{% trans "Product" %}</label>
diff --git a/tcms/testruns/static/testruns/js/mutable.js b/tcms/testruns/static/testruns/js/mutable.js
index c1b249fe06..1ed06b9822 100644
--- a/tcms/testruns/static/testruns/js/mutable.js
+++ b/tcms/testruns/static/testruns/js/mutable.js
@@ -1,6 +1,6 @@
 import { initializeDateTimePicker } from '../../../../static/js/datetime_picker'
 import { jsonRPC } from '../../../../static/js/jsonrpc'
-import { discoverNestedTestPlans, updateSelect, updateTestPlanSelectFromProduct } from '../../../../static/js/utils'
+import { discoverNestedTestPlans, initDuplicateCheck, updateSelect, updateTestPlanSelectFromProduct } from '../../../../static/js/utils'
 
 export function pageTestrunsMutableReadyHandler () {
     initializeDateTimePicker('#id_planned_start')
@@ -42,4 +42,25 @@ export function pageTestrunsMutableReadyHandler () {
     $('#add_id_build').click(function () {
         return showRelatedObjectPopup(this)
     })
+
+    initDuplicateCheck({
+        rpcMethod: 'TestRun.filter',
+        fieldName: 'summary',
+        inputSelector: '#id_summary',
+        groupSelector: '#summary-group',
+        warningSelector: '#duplicate-summary-warning',
+        autocompleteSelector: '#summary-autocomplete',
+        modalSelector: '#duplicate-modal',
+        prefix: 'TR',
+        detailUrlBase: '/runs/',
+        descriptionField: 'notes',
+        modalRows: function (g, tr) {
+            return [
+                [g('trans-duplicate-modal-summary'), tr.summary],
+                [g('trans-duplicate-modal-plan'), tr.plan__name],
+                [g('trans-duplicate-modal-build'), tr.build__name],
+                [g('trans-duplicate-modal-manager'), tr.manager__username]
+            ]
+        }
+    })
 }
diff --git a/tcms/testruns/templates/testruns/mutable.html b/tcms/testruns/templates/testruns/mutable.html
index d215b3c919..93c1e725e9 100644
--- a/tcms/testruns/templates/testruns/mutable.html
+++ b/tcms/testruns/templates/testruns/mutable.html
@@ -19,11 +19,26 @@
     <form class="form-horizontal" action="{% if object %}{% url 'testruns-edit' object.pk %}{% else %}{% url 'testruns-new' %}{% endif %}" method="post">
         {% csrf_token %}
 
-        <div class="form-group">
+        <div class="form-group" id="summary-group"
+            data-trans-duplicate-blocked="{% trans 'A test run with this exact summary already exists. Duplicates are not allowed.' %}"
+            data-trans-duplicate-modal-title="{% trans 'Duplicate test run found' %}"
+            data-trans-duplicate-modal-summary="{% trans 'Summary' %}"
+            data-trans-duplicate-modal-plan="{% trans 'Test plan' %}"
+            data-trans-duplicate-modal-build="{% trans 'Build' %}"
+            data-trans-duplicate-modal-manager="{% trans 'Manager' %}"
+            data-trans-duplicate-modal-text="{% trans 'Notes' %}"
+            data-trans-duplicate-modal-view="{% trans 'View existing test run' %}">
             <label class="col-md-1 col-lg-1" for="id_summary">{% trans "Summary" %}</label>
             <div class="col-md-3 col-lg-3 {% if form.summary.errors %}has-error{% endif %}">
-                <input type="text" id="id_summary" name="summary" value="{{ form.summary.value }}" class="form-control" required>
+                <input type="text" id="id_summary" name="summary" value="{{ form.summary.value }}" class="form-control" required autocomplete="off">
+                {% if not object %}
+                <div id="summary-autocomplete" class="list-group" style="display: none; max-height: 200px; overflow-y: auto; margin-bottom: 0; background-color: #f5f5f5; border: 1px solid #b7b7b7;"></div>
+                {% endif %}
                 {{ form.summary.errors }}
+                {% if not object %}
+                <div id="duplicate-summary-warning" class="help-block hidden kiwi-color-warning">
+                </div>
+                {% endif %}
             </div>
 
             <label class="col-md-1 col-lg-1" for="id_manager">{% trans "Manager" %}</label>
@@ -41,6 +56,10 @@
             </div>
         </div>
 
+        {% if not object %}
+        {% include "include/duplicate_check_modal.html" %}
+        {% endif %}
+
         <div class="form-group">
             <div class="col-md-1 col-lg-1">
                 <label for="id_product">{% trans "Product" %}</label>