diff --git a/packages/core/src/lib/sign-in-experience.test.ts b/packages/core/src/lib/sign-in-experience.test.ts
new file mode 100644
index 000000000..0fc506e1d
--- /dev/null
+++ b/packages/core/src/lib/sign-in-experience.test.ts
@@ -0,0 +1,46 @@
+import { BrandingStyle } from '@logto/schemas';
+
+import RequestError from '@/errors/RequestError';
+import { validateBranding, validateTermsOfUse } from '@/lib/sign-in-experience';
+import { mockBranding } from '@/utils/mock';
+
+describe('validate branding', () => {
+  test('should throw when the UI style contains the slogan and slogan is empty', () => {
+    expect(() => {
+      validateBranding({
+        ...mockBranding,
+        style: BrandingStyle.Logo_Slogan,
+        slogan: '',
+      });
+    }).toMatchError(new RequestError('sign_in_experiences.empty_slogan'));
+  });
+
+  test('should throw when the UI style contains the slogan and slogan is blank', () => {
+    expect(() => {
+      validateBranding({
+        ...mockBranding,
+        style: BrandingStyle.Logo_Slogan,
+        slogan: ' \t\n',
+      });
+    }).toMatchError(new RequestError('sign_in_experiences.empty_slogan'));
+  });
+
+  test('should not throw when the UI style does not contain the slogan and slogan is empty', () => {
+    expect(() => {
+      validateBranding({
+        ...mockBranding,
+        style: BrandingStyle.Logo,
+      });
+    }).not.toThrow();
+  });
+});
+
+describe('validate terms of use', () => {
+  test('should throw when terms of use is enabled and content URL is empty', () => {
+    expect(() => {
+      validateTermsOfUse({
+        enabled: true,
+      });
+    }).toMatchError(new RequestError('sign_in_experiences.empty_content_url_of_terms_of_use'));
+  });
+});
diff --git a/packages/core/src/lib/sign-in-experience.ts b/packages/core/src/lib/sign-in-experience.ts
new file mode 100644
index 000000000..b45898b39
--- /dev/null
+++ b/packages/core/src/lib/sign-in-experience.ts
@@ -0,0 +1,16 @@
+import { Branding, BrandingStyle, TermsOfUse } from '@logto/schemas';
+
+import assertThat from '@/utils/assert-that';
+
+export const validateBranding = (branding: Branding) => {
+  if (branding.style === BrandingStyle.Logo_Slogan) {
+    assertThat(branding.slogan?.trim(), 'sign_in_experiences.empty_slogan');
+  }
+};
+
+export const validateTermsOfUse = (termsOfUse: TermsOfUse) => {
+  assertThat(
+    !termsOfUse.enabled || termsOfUse.contentUrl,
+    'sign_in_experiences.empty_content_url_of_terms_of_use'
+  );
+};
diff --git a/packages/core/src/routes/sign-in-experience.test.ts b/packages/core/src/routes/sign-in-experience.test.ts
index 0fe5872bc..27d5bc329 100644
--- a/packages/core/src/routes/sign-in-experience.test.ts
+++ b/packages/core/src/routes/sign-in-experience.test.ts
@@ -1,6 +1,7 @@
-import { SignInExperience, CreateSignInExperience, BrandingStyle, Branding } from '@logto/schemas';
+import { SignInExperience, CreateSignInExperience, TermsOfUse } from '@logto/schemas';
 
-import { mockSignInExperience } from '@/utils/mock';
+import * as signInExpLib from '@/lib/sign-in-experience';
+import { mockBranding, mockSignInExperience } from '@/utils/mock';
 import { createRequester } from '@/utils/test-utils';
 
 import signInExperiencesRoutes from './sign-in-experience';
@@ -25,34 +26,36 @@ describe('signInExperiences routes', () => {
 
   it('GET /sign-in-exp', async () => {
     const response = await signInExperienceRequester.get('/sign-in-exp');
-    expect(response.status).toEqual(200);
-    expect(response.body).toEqual(mockSignInExperience);
+    expect(response).toMatchObject({
+      status: 200,
+      body: mockSignInExperience,
+    });
   });
 
   it('PATCH /sign-in-exp', async () => {
-    const branding: Branding = {
-      primaryColor: '#000',
-      backgroundColor: '#fff',
-      darkMode: true,
-      darkBackgroundColor: '#000',
-      darkPrimaryColor: '#fff',
-      style: BrandingStyle.Logo,
-      logoUrl: 'http://silverhand.png',
-      slogan: 'silverhand',
-    };
-
+    const termsOfUse: TermsOfUse = { enabled: false };
     const socialSignInConnectorIds = ['abc', 'def'];
 
+    const validateBranding = jest.spyOn(signInExpLib, 'validateBranding');
+    const validateTermsOfUse = jest.spyOn(signInExpLib, 'validateTermsOfUse');
+
     const response = await signInExperienceRequester.patch('/sign-in-exp').send({
-      branding,
+      branding: mockBranding,
+      termsOfUse,
       socialSignInConnectorIds,
     });
 
-    expect(response.status).toEqual(200);
-    expect(response.body).toEqual({
-      ...mockSignInExperience,
-      branding,
-      socialSignInConnectorIds,
+    expect(validateBranding).toHaveBeenCalledWith(mockBranding);
+    expect(validateTermsOfUse).toHaveBeenCalledWith(termsOfUse);
+
+    expect(response).toMatchObject({
+      status: 200,
+      body: {
+        ...mockSignInExperience,
+        branding: mockBranding,
+        termsOfUse,
+        socialSignInConnectorIds,
+      },
     });
   });
 
diff --git a/packages/core/src/routes/sign-in-experience.ts b/packages/core/src/routes/sign-in-experience.ts
index 09e08f9b2..85ea50df6 100644
--- a/packages/core/src/routes/sign-in-experience.ts
+++ b/packages/core/src/routes/sign-in-experience.ts
@@ -1,6 +1,7 @@
 import { SignInExperiences } from '@logto/schemas';
 
 import { getEnabledSocialConnectorIds } from '@/connectors';
+import { validateBranding, validateTermsOfUse } from '@/lib/sign-in-experience';
 import koaGuard from '@/middleware/koa-guard';
 import {
   findDefaultSignInExperience,
@@ -41,10 +42,22 @@ export default function signInExperiencesRoutes<T extends AuthedRouter>(router:
       body: SignInExperiences.createGuard.omit({ id: true }).partial(),
     }),
     async (ctx, next) => {
-      const { body } = ctx.guard;
+      const { branding, termsOfUse } = ctx.guard.body;
 
+      if (branding) {
+        validateBranding(branding);
+      }
+
+      if (termsOfUse) {
+        validateTermsOfUse(termsOfUse);
+      }
+
+      // TODO: validate SignInMethods
+      // TODO: validate socialConnectorIds
+
+      // TODO: Only update socialSignInConnectorIds when social sign-in is enabled.
       ctx.body = await updateDefaultSignInExperience({
-        ...body,
+        ...ctx.guard.body,
       });
 
       return next();
diff --git a/packages/core/src/utils/mock.ts b/packages/core/src/utils/mock.ts
index 320cbf578..a210a60af 100644
--- a/packages/core/src/utils/mock.ts
+++ b/packages/core/src/utils/mock.ts
@@ -20,6 +20,7 @@ import {
   UserLogResult,
   ConnectorType,
   SignInMethodState,
+  Branding,
 } from '@logto/schemas';
 import pick from 'lodash.pick';
 
@@ -370,4 +371,15 @@ export const mockUserLog: UserLog = {
   payload: {},
   createdAt: 10,
 };
+
+export const mockBranding: Branding = {
+  primaryColor: '#000',
+  backgroundColor: '#fff',
+  darkMode: true,
+  darkBackgroundColor: '#000',
+  darkPrimaryColor: '#fff',
+  style: BrandingStyle.Logo_Slogan,
+  logoUrl: 'http://silverhand.png',
+  slogan: 'Silverhand.',
+};
 /* eslint-enable max-lines */
diff --git a/packages/phrases/src/locales/en.ts b/packages/phrases/src/locales/en.ts
index fb89ab7d8..b5b0173dd 100644
--- a/packages/phrases/src/locales/en.ts
+++ b/packages/phrases/src/locales/en.ts
@@ -340,6 +340,12 @@ const errors = {
     expired: 'Passcode has expired. Please request a new passcode.',
     exceed_max_try: 'Passcode verification limitation exceeded. Please request a new passcode.',
   },
+  sign_in_experiences: {
+    empty_content_url_of_terms_of_use:
+      'Empty "Terms of use" content URL. Please add the content URL if "Terms of use" is enabled.',
+    empty_slogan:
+      'Empty branding slogan. Please add a branding slogan if a UI style containing the slogan is selected.',
+  },
   swagger: {
     invalid_zod_type: 'Invalid Zod type, please check route guard config.',
   },
diff --git a/packages/phrases/src/locales/zh-cn.ts b/packages/phrases/src/locales/zh-cn.ts
index 8da91ea26..72e258204 100644
--- a/packages/phrases/src/locales/zh-cn.ts
+++ b/packages/phrases/src/locales/zh-cn.ts
@@ -338,6 +338,11 @@ const errors = {
     expired: '验证码已过期. 请尝试请求新的验证码。',
     exceed_max_try: '超过最大验证次数. 请尝试请求新的验证码。',
   },
+  sign_in_experiences: {
+    empty_content_url_of_terms_of_use:
+      '空的《用户协议》内容链接。当启用《用户协议》时，请添加其内容链接。',
+    empty_slogan: '空的标语。当使用包含标语的 UI 风格时，请添加标语。',
+  },
   swagger: {
     invalid_zod_type: '无效的 Zod 类型，请检查路由 guard 配置。',
   },