diff --git a/x-pack/plugins/stack_connectors/public/connector_types/email/email_params.test.tsx b/x-pack/plugins/stack_connectors/public/connector_types/email/email_params.test.tsx
index 76cc3b136455a..3d772556e7262 100644
--- a/x-pack/plugins/stack_connectors/public/connector_types/email/email_params.test.tsx
+++ b/x-pack/plugins/stack_connectors/public/connector_types/email/email_params.test.tsx
@@ -7,12 +7,13 @@
 
 import React from 'react';
 import { mountWithIntl } from '@kbn/test-jest-helpers';
-import { render, fireEvent, screen } from '@testing-library/react';
+import { render, fireEvent, screen, within } from '@testing-library/react';
 import { __IntlProvider as IntlProvider } from '@kbn/i18n-react';
 import { useKibana } from '@kbn/kibana-react-plugin/public';
 import { triggersActionsUiMock } from '@kbn/triggers-actions-ui-plugin/public/mocks';
 import EmailParamsFields from './email_params';
 import { getIsExperimentalFeatureEnabled } from '../../common/get_experimental_features';
+import { getFormattedEmailOptions } from './email_params';
 
 jest.mock('@kbn/kibana-react-plugin/public', () => ({
   useKibana: jest.fn(),
@@ -28,6 +29,24 @@ const mockKibana = () => {
   });
 };
 
+const emailTestCases = [
+  {
+    field: 'to',
+    fieldValue: 'new1@test.com, new2@test.com , new1@test.com, ',
+    expected: ['test@test.com', 'new1@test.com', 'new2@test.com'],
+  },
+  {
+    field: 'cc',
+    fieldValue: 'newcc1@test.com, newcc2@test.com , newcc1@test.com, ',
+    expected: ['cc@test.com', 'newcc1@test.com', 'newcc2@test.com'],
+  },
+  {
+    field: 'bcc',
+    fieldValue: 'newbcc1@test.com, newbcc2@test.com , newbcc1@test.com, ',
+    expected: ['bcc@test.com', 'newbcc1@test.com', 'newbcc2@test.com'],
+  },
+];
+
 describe('EmailParamsFields renders', () => {
   beforeEach(() => {
     jest.clearAllMocks();
@@ -62,6 +81,40 @@ describe('EmailParamsFields renders', () => {
     expect(await screen.findByTestId('messageTextArea')).toBeVisible();
   });
 
+  emailTestCases.forEach(({ field, fieldValue, expected }) => {
+    test(`"${field}" field value updates correctly when comma-separated emails are pasted`, async () => {
+      const actionParams = {
+        cc: ['cc@test.com'],
+        bcc: ['bcc@test.com'],
+        to: ['test@test.com'],
+        subject: 'test',
+        message: 'test message',
+      };
+
+      const editAction = jest.fn();
+
+      render(
+        <IntlProvider locale="en">
+          <EmailParamsFields
+            actionParams={actionParams}
+            errors={{ to: [], cc: [], bcc: [], subject: [], message: [] }}
+            editAction={editAction}
+            defaultMessage={'Some default message'}
+            index={0}
+          />
+        </IntlProvider>
+      );
+
+      const euiComboBox = screen.getByTestId(`${field}EmailAddressInput`);
+      const input = within(euiComboBox).getByTestId('comboBoxSearchInput');
+      fireEvent.change(input, { target: { value: fieldValue } });
+      expect(input).toHaveValue(fieldValue);
+
+      fireEvent.keyDown(input, { key: 'Enter', code: 'Enter' });
+      expect(editAction).toHaveBeenCalledWith(field, expected, 0);
+    });
+  });
+
   test('message param field is rendered with default value if not set', () => {
     const actionParams = {
       cc: [],
@@ -234,3 +287,48 @@ describe('EmailParamsFields renders', () => {
     expect(editAction).not.toHaveBeenCalled();
   });
 });
+
+describe('getFormattedEmailOptions', () => {
+  test('should return new options added to previous options', () => {
+    const searchValue = 'test@test.com, other@test.com';
+    const previousOptions = [{ label: 'existing@test.com' }];
+    const newOptions = getFormattedEmailOptions(searchValue, previousOptions);
+
+    expect(newOptions).toEqual([
+      { label: 'existing@test.com' },
+      { label: 'test@test.com' },
+      { label: 'other@test.com' },
+    ]);
+  });
+
+  test('should trim extra spaces in search value', () => {
+    const searchValue = ' test@test.com ,  other@test.com   ,   ';
+    const previousOptions: Array<{ label: string }> = [];
+    const newOptions = getFormattedEmailOptions(searchValue, previousOptions);
+
+    expect(newOptions).toEqual([{ label: 'test@test.com' }, { label: 'other@test.com' }]);
+  });
+
+  test('should prevent duplicate email addresses', () => {
+    const searchValue = 'duplicate@test.com, duplicate@test.com';
+    const previousOptions = [{ label: 'existing@test.com' }, { label: 'duplicate@test.com' }];
+    const newOptions = getFormattedEmailOptions(searchValue, previousOptions);
+
+    expect(newOptions).toEqual([{ label: 'existing@test.com' }, { label: 'duplicate@test.com' }]);
+  });
+
+  test('should return previous options if search value is empty', () => {
+    const searchValue = '';
+    const previousOptions = [{ label: 'existing@test.com' }];
+    const newOptions = getFormattedEmailOptions(searchValue, previousOptions);
+    expect(newOptions).toEqual([{ label: 'existing@test.com' }]);
+  });
+
+  test('should handle single email without comma', () => {
+    const searchValue = 'single@test.com';
+    const previousOptions = [{ label: 'existing@test.com' }];
+    const newOptions = getFormattedEmailOptions(searchValue, previousOptions);
+
+    expect(newOptions).toEqual([{ label: 'existing@test.com' }, { label: 'single@test.com' }]);
+  });
+});
diff --git a/x-pack/plugins/stack_connectors/public/connector_types/email/email_params.tsx b/x-pack/plugins/stack_connectors/public/connector_types/email/email_params.tsx
index d9a4750cb4564..745349ab5e872 100644
--- a/x-pack/plugins/stack_connectors/public/connector_types/email/email_params.tsx
+++ b/x-pack/plugins/stack_connectors/public/connector_types/email/email_params.tsx
@@ -18,6 +18,21 @@ import { EmailActionParams } from '../types';
 
 const noop = () => {};
 
+export const getFormattedEmailOptions = (
+  searchValue: string,
+  previousOptions: Array<{ label: string }>
+): Array<{ label: string }> => {
+  if (!searchValue.trim()) return previousOptions;
+  const previousEmails: string[] = previousOptions.map((option) => option.label);
+  const allUniqueEmails: Set<string> = new Set(previousEmails);
+  searchValue.split(',').forEach((email) => {
+    const trimmedEmail = email.trim();
+    if (trimmedEmail) allUniqueEmails.add(trimmedEmail);
+  });
+  const formattedOptions = Array.from(allUniqueEmails).map((email) => ({ label: email }));
+  return formattedOptions;
+};
+
 export const EmailParamsFields = ({
   actionParams,
   editAction,
@@ -105,7 +120,7 @@ export const EmailParamsFields = ({
           data-test-subj="toEmailAddressInput"
           selectedOptions={toOptions}
           onCreateOption={(searchValue: string) => {
-            const newOptions = [...toOptions, { label: searchValue }];
+            const newOptions = getFormattedEmailOptions(searchValue, toOptions);
             editAction(
               'to',
               newOptions.map((newOption) => newOption.label),
@@ -148,7 +163,7 @@ export const EmailParamsFields = ({
             data-test-subj="ccEmailAddressInput"
             selectedOptions={ccOptions}
             onCreateOption={(searchValue: string) => {
-              const newOptions = [...ccOptions, { label: searchValue }];
+              const newOptions = getFormattedEmailOptions(searchValue, ccOptions);
               editAction(
                 'cc',
                 newOptions.map((newOption) => newOption.label),
@@ -192,7 +207,7 @@ export const EmailParamsFields = ({
             data-test-subj="bccEmailAddressInput"
             selectedOptions={bccOptions}
             onCreateOption={(searchValue: string) => {
-              const newOptions = [...bccOptions, { label: searchValue }];
+              const newOptions = getFormattedEmailOptions(searchValue, bccOptions);
               editAction(
                 'bcc',
                 newOptions.map((newOption) => newOption.label),