diff --git a/packages/core-base/src/context.ts b/packages/core-base/src/context.ts
index 4a49ea0a1..2572b34d9 100644
--- a/packages/core-base/src/context.ts
+++ b/packages/core-base/src/context.ts
@@ -3,6 +3,7 @@
 import {
   assign,
   create,
+  deepCopy,
   isArray,
   isBoolean,
   isFunction,
@@ -431,6 +432,7 @@ export const getFallbackContext = (): CoreContext | null => _fallbackContext
 // ID for CoreContext
 let _cid = 0
 
+// TODO: API documentation, if `@intlify/core` will be documented as a separate package
 export function createCoreContext<
   Message = string,
   Options extends CoreOptions<Message> = CoreOptions<Message>,
@@ -631,6 +633,33 @@ export function createCoreContext<Message = string>(options: any = {}): any {
 
 const createResources = (locale: Locale) => ({ [locale]: create() })
 
+// TODO: API documentation, if `@intlify/core` will be documented as a separate package
+export function getLocaleMessage<
+  Context extends CoreContext,
+  Locales = keyof Context['messages'],
+  Return = Context['messages'][keyof Context['messages']]
+>(ctx: Context, locale: Locales): Return | undefined {
+  const src = (ctx.messages as any)[locale]
+  if (src == null) {
+    return undefined
+  }
+  const dest = create()
+  deepCopy(src, dest)
+  return dest as Return
+}
+
+// TODO: API documentation, if `@intlify/core` will be documented as a separate package
+export function setLocaleMessage<
+  Context extends CoreContext,
+  Locales = keyof Context['messages']
+>(
+  ctx: Context,
+  locale: Locales,
+  messages: Context['messages'][keyof Context['messages']]
+): void {
+  ;(ctx.messages as any)[locale] = messages
+}
+
 /** @internal */
 export function isTranslateFallbackWarn(
   fallback: boolean | RegExp,
diff --git a/packages/core-base/test/context.test-d.ts b/packages/core-base/test/context.test-d.ts
index b0987e76c..ab9c69491 100644
--- a/packages/core-base/test/context.test-d.ts
+++ b/packages/core-base/test/context.test-d.ts
@@ -1,4 +1,4 @@
-import { createCoreContext } from '../src'
+import { createCoreContext, getLocaleMessage } from '../src'
 
 import type {
   DateTimeFormat,
@@ -129,6 +129,10 @@ test('strict context', () => {
     en: NumberFormat
     ja: NumberFormat
   }>()
+
+  expectTypeOf(getLocaleMessage(strictCtx, 'en')).toEqualTypeOf<
+    ResourceSchema | undefined
+  >()
 })
 
 test('strict context with direct options', () => {
@@ -198,6 +202,10 @@ test('strict context with direct options', () => {
     }
   }>()
 
+  expectTypeOf(getLocaleMessage(strictDirectCtx, 'en')).toEqualTypeOf<
+    ResourceSchema | undefined
+  >()
+
   const nullCtx1 = createCoreContext({})
   expectTypeOf(nullCtx1.locale).toEqualTypeOf<Locale | LocaleDetector>()
   nullCtx1.locale = 'ja'
diff --git a/packages/core-base/test/context.test.ts b/packages/core-base/test/context.test.ts
index 8b7b3df94..bed37cb50 100644
--- a/packages/core-base/test/context.test.ts
+++ b/packages/core-base/test/context.test.ts
@@ -1,4 +1,8 @@
-import { createCoreContext as context } from '../src/context'
+import {
+  createCoreContext as context,
+  getLocaleMessage,
+  setLocaleMessage
+} from '../src/context'
 
 describe('locale', () => {
   test('default', () => {
@@ -170,3 +174,39 @@ describe('escapeParameter', () => {
     expect(ctx.escapeParameter).toEqual(true)
   })
 })
+
+describe('getLocaleMessage', () => {
+  test('exist locale', () => {
+    const ctx = context({
+      messages: {
+        en: { hello: 'hello' },
+        ja: { hello: 'こんにちは！' }
+      }
+    })
+    const messages = getLocaleMessage(ctx, 'en')
+    expect(messages).toEqual({ hello: 'hello' })
+  })
+
+  test('not exist locale', () => {
+    const ctx = context({
+      locale: 'en',
+      messages: {
+        en: { hello: 'hello' }
+      }
+    })
+    const messages = getLocaleMessage(ctx, 'ja')
+    expect(messages).toBeUndefined()
+  })
+})
+
+test('setMessages', () => {
+  const ctx = context({
+    locale: 'en',
+    messages: {
+      en: { hello: 'hello' }
+    }
+  })
+
+  setLocaleMessage(ctx, 'ja', { hello: 'こんにちは！' })
+  expect(getLocaleMessage(ctx, 'ja')).toMatchObject({ hello: 'こんにちは！' })
+})