diff --git a/x-pack/plugins/actions/server/builtin_action_types/pagerduty.test.ts b/x-pack/plugins/actions/server/builtin_action_types/pagerduty.test.ts
index f3c64889e08a9..e406b37ae61fb 100644
--- a/x-pack/plugins/actions/server/builtin_action_types/pagerduty.test.ts
+++ b/x-pack/plugins/actions/server/builtin_action_types/pagerduty.test.ts
@@ -169,6 +169,16 @@ describe('validateParams()', () => {
       });
     }).toThrowError(`error validating action params: error parsing timestamp "${timestamp}"`);
   });
+
+  test('should validate and throw error when dedupKey is missing on resolve', () => {
+    expect(() => {
+      validateParams(actionType, {
+        eventAction: 'resolve',
+      });
+    }).toThrowError(
+      `error validating action params: DedupKey is required when eventAction is "resolve"`
+    );
+  });
 });
 
 describe('execute()', () => {
diff --git a/x-pack/plugins/actions/server/builtin_action_types/pagerduty.ts b/x-pack/plugins/actions/server/builtin_action_types/pagerduty.ts
index 84960c023bd2f..a1a0bb0461315 100644
--- a/x-pack/plugins/actions/server/builtin_action_types/pagerduty.ts
+++ b/x-pack/plugins/actions/server/builtin_action_types/pagerduty.ts
@@ -51,6 +51,10 @@ export type ActionParamsType = TypeOf<typeof ParamsSchema>;
 const EVENT_ACTION_TRIGGER = 'trigger';
 const EVENT_ACTION_RESOLVE = 'resolve';
 const EVENT_ACTION_ACKNOWLEDGE = 'acknowledge';
+const EVENT_ACTIONS_WITH_REQUIRED_DEDUPKEY = new Set([
+  EVENT_ACTION_RESOLVE,
+  EVENT_ACTION_ACKNOWLEDGE,
+]);
 
 const EventActionSchema = schema.oneOf([
   schema.literal(EVENT_ACTION_TRIGGER),
@@ -81,7 +85,7 @@ const ParamsSchema = schema.object(
 );
 
 function validateParams(paramsObject: unknown): string | void {
-  const { timestamp } = paramsObject as ActionParamsType;
+  const { timestamp, eventAction, dedupKey } = paramsObject as ActionParamsType;
   if (timestamp != null) {
     try {
       const date = Date.parse(timestamp);
@@ -103,6 +107,14 @@ function validateParams(paramsObject: unknown): string | void {
       });
     }
   }
+  if (EVENT_ACTIONS_WITH_REQUIRED_DEDUPKEY.has(eventAction) && !dedupKey) {
+    return i18n.translate('xpack.actions.builtin.pagerduty.missingDedupkeyErrorMessage', {
+      defaultMessage: `DedupKey is required when eventAction is "{eventAction}"`,
+      values: {
+        eventAction,
+      },
+    });
+  }
 }
 
 // action type definition
diff --git a/x-pack/plugins/alerts/server/saved_objects/migrations.test.ts b/x-pack/plugins/alerts/server/saved_objects/migrations.test.ts
index 1c1261ae3fa08..10e1a9ae421b7 100644
--- a/x-pack/plugins/alerts/server/saved_objects/migrations.test.ts
+++ b/x-pack/plugins/alerts/server/saved_objects/migrations.test.ts
@@ -85,6 +85,120 @@ describe('7.10.0', () => {
       },
     });
   });
+
+  test('migrates PagerDuty actions to set a default dedupkey of the AlertId', () => {
+    const migration710 = getMigrations(encryptedSavedObjectsSetup)['7.10.0'];
+    const alert = getMockData({
+      actions: [
+        {
+          actionTypeId: '.pagerduty',
+          group: 'default',
+          params: {
+            summary: 'fired {{alertInstanceId}}',
+            eventAction: 'resolve',
+            component: '',
+          },
+          id: 'b62ea790-5366-4abc-a7df-33db1db78410',
+        },
+      ],
+    });
+    expect(migration710(alert, { log })).toMatchObject({
+      ...alert,
+      attributes: {
+        ...alert.attributes,
+        actions: [
+          {
+            actionTypeId: '.pagerduty',
+            group: 'default',
+            params: {
+              summary: 'fired {{alertInstanceId}}',
+              eventAction: 'resolve',
+              dedupKey: '{{alertId}}',
+              component: '',
+            },
+            id: 'b62ea790-5366-4abc-a7df-33db1db78410',
+          },
+        ],
+      },
+    });
+  });
+
+  test('skips PagerDuty actions with a specified dedupkey', () => {
+    const migration710 = getMigrations(encryptedSavedObjectsSetup)['7.10.0'];
+    const alert = getMockData({
+      actions: [
+        {
+          actionTypeId: '.pagerduty',
+          group: 'default',
+          params: {
+            summary: 'fired {{alertInstanceId}}',
+            eventAction: 'trigger',
+            dedupKey: '{{alertInstanceId}}',
+            component: '',
+          },
+          id: 'b62ea790-5366-4abc-a7df-33db1db78410',
+        },
+      ],
+    });
+    expect(migration710(alert, { log })).toMatchObject({
+      ...alert,
+      attributes: {
+        ...alert.attributes,
+        actions: [
+          {
+            actionTypeId: '.pagerduty',
+            group: 'default',
+            params: {
+              summary: 'fired {{alertInstanceId}}',
+              eventAction: 'trigger',
+              dedupKey: '{{alertInstanceId}}',
+              component: '',
+            },
+            id: 'b62ea790-5366-4abc-a7df-33db1db78410',
+          },
+        ],
+      },
+    });
+  });
+
+  test('skips PagerDuty actions with an eventAction of "trigger"', () => {
+    const migration710 = getMigrations(encryptedSavedObjectsSetup)['7.10.0'];
+    const alert = getMockData({
+      actions: [
+        {
+          actionTypeId: '.pagerduty',
+          group: 'default',
+          params: {
+            summary: 'fired {{alertInstanceId}}',
+            eventAction: 'trigger',
+            component: '',
+          },
+          id: 'b62ea790-5366-4abc-a7df-33db1db78410',
+        },
+      ],
+    });
+    expect(migration710(alert, { log })).toEqual({
+      ...alert,
+      attributes: {
+        ...alert.attributes,
+        meta: {
+          versionApiKeyLastmodified: 'pre-7.10.0',
+        },
+        actions: [
+          {
+            actionTypeId: '.pagerduty',
+            group: 'default',
+            params: {
+              summary: 'fired {{alertInstanceId}}',
+              eventAction: 'trigger',
+              component: '',
+            },
+            id: 'b62ea790-5366-4abc-a7df-33db1db78410',
+          },
+        ],
+      },
+    });
+  });
 });
 
 describe('7.10.0 migrates with failure', () => {
diff --git a/x-pack/plugins/alerts/server/saved_objects/migrations.ts b/x-pack/plugins/alerts/server/saved_objects/migrations.ts
index c88f4d786c212..537c21e85c0bd 100644
--- a/x-pack/plugins/alerts/server/saved_objects/migrations.ts
+++ b/x-pack/plugins/alerts/server/saved_objects/migrations.ts
@@ -18,10 +18,20 @@ import {
 
 export const LEGACY_LAST_MODIFIED_VERSION = 'pre-7.10.0';
 
+type AlertMigration = (
+  doc: SavedObjectUnsanitizedDoc<RawAlert>
+) => SavedObjectUnsanitizedDoc<RawAlert>;
+
 export function getMigrations(
   encryptedSavedObjects: EncryptedSavedObjectsPluginSetup
 ): SavedObjectMigrationMap {
-  const migrationWhenRBACWasIntroduced = markAsLegacyAndChangeConsumer(encryptedSavedObjects);
+  const migrationWhenRBACWasIntroduced = encryptedSavedObjects.createMigration<RawAlert, RawAlert>(
+    function shouldBeMigrated(doc): doc is SavedObjectUnsanitizedDoc<RawAlert> {
+      // migrate all documents in 7.10 in order to add the "meta" RBAC field
+      return true;
+    },
+    pipeMigrations(markAsLegacyAndChangeConsumer, setAlertIdAsDefaultDedupkeyOnPagerDutyActions)
+  );
 
   return {
     '7.10.0': executeMigrationWithErrorHandling(migrationWhenRBACWasIntroduced, '7.10.0'),
@@ -52,29 +62,55 @@ const consumersToChange: Map<string, string> = new Map(
     [SIEM_APP_ID]: SIEM_SERVER_APP_ID,
   })
 );
+
 function markAsLegacyAndChangeConsumer(
-  encryptedSavedObjects: EncryptedSavedObjectsPluginSetup
-): SavedObjectMigrationFn<RawAlert, RawAlert> {
-  return encryptedSavedObjects.createMigration<RawAlert, RawAlert>(
-    function shouldBeMigrated(doc): doc is SavedObjectUnsanitizedDoc<RawAlert> {
-      // migrate all documents in 7.10 in order to add the "meta" RBAC field
-      return true;
+  doc: SavedObjectUnsanitizedDoc<RawAlert>
+): SavedObjectUnsanitizedDoc<RawAlert> {
+  const {
+    attributes: { consumer },
+  } = doc;
+  return {
+    ...doc,
+    attributes: {
+      ...doc.attributes,
+      consumer: consumersToChange.get(consumer) ?? consumer,
+      // mark any alert predating 7.10 as a legacy alert
+      meta: {
+        versionApiKeyLastmodified: LEGACY_LAST_MODIFIED_VERSION,
+      },
     },
-    (doc: SavedObjectUnsanitizedDoc<RawAlert>): SavedObjectUnsanitizedDoc<RawAlert> => {
-      const {
-        attributes: { consumer },
-      } = doc;
-      return {
-        ...doc,
-        attributes: {
-          ...doc.attributes,
-          consumer: consumersToChange.get(consumer) ?? consumer,
-          // mark any alert predating 7.10 as a legacy alert
-          meta: {
-            versionApiKeyLastmodified: LEGACY_LAST_MODIFIED_VERSION,
-          },
-        },
-      };
-    }
-  );
+  };
+}
+
+function setAlertIdAsDefaultDedupkeyOnPagerDutyActions(
+  doc: SavedObjectUnsanitizedDoc<RawAlert>
+): SavedObjectUnsanitizedDoc<RawAlert> {
+  const { attributes } = doc;
+  return {
+    ...doc,
+    attributes: {
+      ...attributes,
+      ...(attributes.actions
+        ? {
+            actions: attributes.actions.map((action) => {
+              if (action.actionTypeId !== '.pagerduty' || action.params.eventAction === 'trigger') {
+                return action;
+              }
+              return {
+                ...action,
+                params: {
+                  ...action.params,
+                  dedupKey: action.params.dedupKey ?? '{{alertId}}',
+                },
+              };
+            }),
+          }
+        : {}),
+    },
+  };
+}
+
+function pipeMigrations(...migrations: AlertMigration[]): AlertMigration {
+  return (doc: SavedObjectUnsanitizedDoc<RawAlert>) =>
+    migrations.reduce((migratedDoc, nextMigration) => nextMigration(migratedDoc), doc);
 }
diff --git a/x-pack/plugins/triggers_actions_ui/public/application/components/builtin_action_types/pagerduty/pagerduty.tsx b/x-pack/plugins/triggers_actions_ui/public/application/components/builtin_action_types/pagerduty/pagerduty.tsx
index 90d8da346c71d..03bfbb38da6f2 100644
--- a/x-pack/plugins/triggers_actions_ui/public/application/components/builtin_action_types/pagerduty/pagerduty.tsx
+++ b/x-pack/plugins/triggers_actions_ui/public/application/components/builtin_action_types/pagerduty/pagerduty.tsx
@@ -50,8 +50,22 @@ export function getActionType(): ActionTypeModel {
       const errors = {
         summary: new Array<string>(),
         timestamp: new Array<string>(),
+        dedupKey: new Array<string>(),
       };
       validationResult.errors = errors;
+      if (
+        !actionParams.dedupKey?.length &&
+        (actionParams.eventAction === 'resolve' || actionParams.eventAction === 'acknowledge')
+      ) {
+        errors.dedupKey.push(
+          i18n.translate(
+            'xpack.triggersActionsUI.components.builtinActionTypes.pagerDutyAction.error.requiredDedupKeyText',
+            {
+              defaultMessage: 'DedupKey is required when resolving or acknowledging an incident.',
+            }
+          )
+        );
+      }
       if (!actionParams.summary?.length) {
         errors.summary.push(
           i18n.translate(
diff --git a/x-pack/plugins/triggers_actions_ui/public/application/components/builtin_action_types/pagerduty/pagerduty_params.tsx b/x-pack/plugins/triggers_actions_ui/public/application/components/builtin_action_types/pagerduty/pagerduty_params.tsx
index c8ad5f5b7080e..39800865ed761 100644
--- a/x-pack/plugins/triggers_actions_ui/public/application/components/builtin_action_types/pagerduty/pagerduty_params.tsx
+++ b/x-pack/plugins/triggers_actions_ui/public/application/components/builtin_action_types/pagerduty/pagerduty_params.tsx
@@ -94,6 +94,9 @@ const PagerDutyParamsFields: React.FunctionComponent<ActionParamsProps<PagerDuty
       ),
     },
   ];
+
+  const isDedupeKeyRequired = eventAction !== 'trigger';
+
   return (
     <Fragment>
       <EuiFlexGroup>
@@ -144,12 +147,23 @@ const PagerDutyParamsFields: React.FunctionComponent<ActionParamsProps<PagerDuty
         <EuiFlexItem>
           <EuiFormRow
             fullWidth
-            label={i18n.translate(
-              'xpack.triggersActionsUI.components.builtinActionTypes.pagerDutyAction.dedupKeyTextFieldLabel',
-              {
-                defaultMessage: 'DedupKey (optional)',
-              }
-            )}
+            error={errors.dedupKey}
+            isInvalid={errors.dedupKey.length > 0}
+            label={
+              isDedupeKeyRequired
+                ? i18n.translate(
+                    'xpack.triggersActionsUI.components.builtinActionTypes.pagerDutyAction.dedupKeyTextRequiredFieldLabel',
+                    {
+                      defaultMessage: 'DedupKey',
+                    }
+                  )
+                : i18n.translate(
+                    'xpack.triggersActionsUI.components.builtinActionTypes.pagerDutyAction.dedupKeyTextFieldLabel',
+                    {
+                      defaultMessage: 'DedupKey (optional)',
+                    }
+                  )
+            }
           >
             <TextFieldWithMessageVariables
               index={index}
diff --git a/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/migrations.ts b/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/migrations.ts
index 81f7c8c97ba8c..4e9494819b8a7 100644
--- a/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/migrations.ts
+++ b/x-pack/test/alerting_api_integration/spaces_only/tests/alerting/migrations.ts
@@ -5,9 +5,15 @@
  */
 
 import expect from '@kbn/expect';
+import uuid from 'uuid';
 import { getUrlPrefix } from '../../../common/lib';
 import { FtrProviderContext } from '../../../common/ftr_provider_context';
 
+import {
+  getExternalServiceSimulatorPath,
+  ExternalServiceSimulator,
+} from '../../../common/fixtures/plugins/actions_simulators/server/plugin';
+
 // eslint-disable-next-line import/no-default-export
 export default function createGetTests({ getService }: FtrProviderContext) {
   const supertest = getService('supertest');
@@ -39,5 +45,49 @@ export default function createGetTests({ getService }: FtrProviderContext) {
       expect(response.status).to.eql(200);
       expect(response.body.consumer).to.equal('infrastructure');
     });
+
+    it('7.10.0 migrates PagerDuty actions to have a default dedupKey', async () => {
+      const response = await supertest.get(
+        `${getUrlPrefix(``)}/api/alerts/alert/b6087f72-994f-46fb-8120-c6e5c50d0f8f`
+      );
+
+      expect(response.status).to.eql(200);
+
+      expect(response.body.actions).to.eql([
+        {
+          actionTypeId: '.pagerduty',
+          id: 'a6a8ab7a-35cf-445e-ade3-215a029c2ee3',
+          group: 'default',
+          params: {
+            component: '',
+            dedupKey: '{{alertId}}',
+            eventAction: 'trigger',
+            summary: 'fired {{alertInstanceId}}',
+          },
+        },
+        {
+          actionTypeId: '.pagerduty',
+          id: 'a6a8ab7a-35cf-445e-ade3-215a029c2ee3',
+          group: 'default',
+          params: {
+            component: '',
+            dedupKey: '{{alertId}}',
+            eventAction: 'resolve',
+            summary: 'fired {{alertInstanceId}}',
+          },
+        },
+        {
+          actionTypeId: '.pagerduty',
+          id: 'a6a8ab7a-35cf-445e-ade3-215a029c2ee3',
+          group: 'default',
+          params: {
+            component: '',
+            dedupKey: '{{alertInstanceId}}',
+            eventAction: 'resolve',
+            summary: 'fired {{alertInstanceId}}',
+          },
+        },
+      ]);
+    });
   });
 }
diff --git a/x-pack/test/functional/es_archives/alerts/data.json b/x-pack/test/functional/es_archives/alerts/data.json
index cc246b0fe44da..4e879116d8cda 100644
--- a/x-pack/test/functional/es_archives/alerts/data.json
+++ b/x-pack/test/functional/es_archives/alerts/data.json
@@ -80,4 +80,115 @@
       "updated_at": "2020-06-17T15:35:39.839Z"
     }
   }
+}
+
+{
+  "type": "doc",
+  "value": {
+    "id": "action:a6a8ab7a-35cf-445e-ade3-215a029c2ee3",
+    "index": ".kibana_1",
+    "source": {
+      "action": {
+        "actionTypeId": ".pagerduty",
+        "config": {
+          "apiUrl": "http://elastic:changeme@localhost:5620/api/_actions-FTS-external-service-simulators/pagerduty"
+        },
+        "name": "A pagerduty action",
+        "secrets": "kvjaTWYKGmCqptyv4giaN+nQGgsZrKXmlULcbAP8KK3JmR8Ei9ADqh5mB+uVC+x+Q7/vTQ5SKZCj3dHv3pmNzZ5WGyZYQFBaaa63Mkp3kIcnpE1OdSAv+3Z/Y+XihHAM19zUm3JRpojnIpYegoS5/vMx1sOzcf/+miYUuZw2lgo0lNE="
+      },
+      "references": [
+      ],
+      "type": "action",
+      "updated_at": "2020-09-22T15:16:06.924Z"
+    }
+  }
+}
+
+{
+  "type": "doc",
+  "value": {
+    "id": "alert:b6087f72-994f-46fb-8120-c6e5c50d0f8f",
+    "index": ".kibana_1",
+    "source": {
+      "alert": {
+        "actions": [
+          {
+            "actionRef": "action_0",
+            "actionTypeId": ".pagerduty",
+            "group": "default",
+            "params": {
+              "component": "",
+              "eventAction": "trigger",
+              "summary": "fired {{alertInstanceId}}"
+            }
+          },
+          {
+            "actionRef": "action_1",
+            "actionTypeId": ".pagerduty",
+            "group": "default",
+            "params": {
+              "component": "",
+              "eventAction": "resolve",
+              "summary": "fired {{alertInstanceId}}"
+            }
+          },
+          {
+            "actionRef": "action_2",
+            "actionTypeId": ".pagerduty",
+            "group": "default",
+            "params": {
+              "component": "",
+              "dedupKey": "{{alertInstanceId}}",
+              "eventAction": "resolve",
+              "summary": "fired {{alertInstanceId}}"
+            }
+          }
+        ],
+        "alertTypeId": "test.noop",
+        "apiKey": null,
+        "apiKeyOwner": null,
+        "consumer": "alertsFixture",
+        "createdAt": "2020-09-22T15:16:07.451Z",
+        "createdBy": null,
+        "enabled": true,
+        "muteAll": false,
+        "mutedInstanceIds": [
+        ],
+        "name": "abc",
+        "params": {
+        },
+        "schedule": {
+          "interval": "1m"
+        },
+        "scheduledTaskId": "8a7c6ff0-fce6-11ea-a888-9337d77a2c25",
+        "tags": [
+          "foo"
+        ],
+        "throttle": "1m",
+        "updatedBy": null
+      },
+      "migrationVersion": {
+        "alert": "7.9.0"
+      },
+      "references": [
+        {
+          "id": "a6a8ab7a-35cf-445e-ade3-215a029c2ee3",
+          "name": "action_0",
+          "type": "action"
+        },
+        {
+          "id": "a6a8ab7a-35cf-445e-ade3-215a029c2ee3",
+          "name": "action_1",
+          "type": "action"
+        },
+        {
+          "id": "a6a8ab7a-35cf-445e-ade3-215a029c2ee3",
+          "name": "action_2",
+          "type": "action"
+        }
+      ],
+      "type": "alert",
+      "updated_at": "2020-09-22T15:16:08.456Z"
+    }
+  }
 }
\ No newline at end of file