diff --git a/packages/manager/.changeset/pr-10110-tests-1706208561568.md b/packages/manager/.changeset/pr-10110-tests-1706208561568.md
new file mode 100644
index 00000000000..49a1409e99b
--- /dev/null
+++ b/packages/manager/.changeset/pr-10110-tests-1706208561568.md
@@ -0,0 +1,5 @@
+---
+"@linode/manager": Tests
+---
+
+Add Cypress tests for account switching from Parent to Child ([#10110](https://github.com/linode/manager/pull/10110))
diff --git a/packages/manager/cypress/e2e/core/parentChild/account-switching.spec.ts b/packages/manager/cypress/e2e/core/parentChild/account-switching.spec.ts
new file mode 100644
index 00000000000..60c6488ef30
--- /dev/null
+++ b/packages/manager/cypress/e2e/core/parentChild/account-switching.spec.ts
@@ -0,0 +1,303 @@
+import {
+  accountFactory,
+  appTokenFactory,
+  profileFactory,
+} from '@src/factories';
+import { accountUserFactory } from '@src/factories/accountUsers';
+import { DateTime } from 'luxon';
+import {
+  mockCreateChildAccountToken,
+  mockCreateChildAccountTokenError,
+  mockGetAccount,
+  mockGetChildAccounts,
+  mockGetChildAccountsError,
+  mockGetUser,
+} from 'support/intercepts/account';
+import { mockGetEvents, mockGetNotifications } from 'support/intercepts/events';
+import {
+  mockAppendFeatureFlags,
+  mockGetFeatureFlagClientstream,
+} from 'support/intercepts/feature-flags';
+import { mockAllApiRequests } from 'support/intercepts/general';
+import { mockGetLinodes } from 'support/intercepts/linodes';
+import { mockGetProfile } from 'support/intercepts/profile';
+import { mockGetRegions } from 'support/intercepts/regions';
+import { ui } from 'support/ui';
+import { makeFeatureFlagData } from 'support/util/feature-flags';
+import { assertLocalStorageValue } from 'support/util/local-storage';
+import { randomLabel, randomNumber, randomString } from 'support/util/random';
+
+/**
+ * Confirms expected username and company name are shown in user menu button and yields the button.
+ *
+ * @param username - Username to expect in user menu button.
+ * @param companyName - Company name to expect in user menu button.
+ *
+ * @returns Cypress chainable that yields the user menu button.
+ */
+const assertUserMenuButton = (username: string, companyName: string) => {
+  return ui.userMenuButton
+    .find()
+    .should('be.visible')
+    .within(() => {
+      cy.findByText(username).should('be.visible');
+      cy.findByText(companyName).should('be.visible');
+    });
+};
+
+/**
+ * Confirms that expected authentication values are set in Local Storage.
+ *
+ * @param token - Authentication token value to assert.
+ * @param expiry - Authentication expiry value to assert.
+ * @param scopes - Authentication scope value to assert.
+ */
+const assertAuthLocalStorage = (
+  token: string,
+  expiry: string,
+  scopes: string
+) => {
+  assertLocalStorageValue('authentication/token', token);
+  assertLocalStorageValue('authentication/expire', expiry);
+  assertLocalStorageValue('authentication/scopes', scopes);
+};
+
+const mockParentAccount = accountFactory.build({
+  company: 'Parent Company',
+});
+
+const mockParentProfile = profileFactory.build({
+  username: randomLabel(),
+  user_type: 'parent',
+});
+
+const mockParentUser = accountUserFactory.build({
+  username: mockParentProfile.username,
+  user_type: 'parent',
+});
+
+const mockChildAccount = accountFactory.build({
+  company: 'Child Company',
+});
+
+const mockChildAccountToken = appTokenFactory.build({
+  id: randomNumber(),
+  created: DateTime.now().toISO(),
+  expiry: DateTime.now().plus({ hours: 1 }).toISO(),
+  label: `${mockChildAccount.company}_proxy`,
+  scopes: '*',
+  token: randomString(32),
+  website: undefined,
+  thumbnail_url: undefined,
+});
+
+const mockErrorMessage = 'An unknown error has occurred.';
+
+describe('Parent/Child account switching', () => {
+  /*
+   * Tests to confirm that Parent account users can switch to Child accounts as expected.
+   */
+  describe('From Parent to Proxy', () => {
+    beforeEach(() => {
+      // @TODO M3-7554, M3-7559: Remove feature flag mocks after feature launch and clean-up.
+      mockAppendFeatureFlags({
+        parentChildAccountAccess: makeFeatureFlagData(true),
+      });
+      mockGetFeatureFlagClientstream();
+    });
+
+    /*
+     * - Confirms that Parent account user can switch to Child account from Account Billing page.
+     * - Confirms that Child account information is displayed in user menu button after switch.
+     * - Confirms that Cloud updates local storage auth values upon account switch.
+     */
+    it('can switch from Parent account to Child account from Billing page', () => {
+      mockGetProfile(mockParentProfile);
+      mockGetAccount(mockParentAccount);
+      mockGetChildAccounts([mockChildAccount]);
+      mockGetUser(mockParentUser);
+
+      cy.visitWithLogin('/account/billing');
+
+      // Confirm that "Switch Account" button is present, then click it.
+      ui.button
+        .findByTitle('Switch Account')
+        .should('be.visible')
+        .should('be.enabled')
+        .click();
+
+      mockCreateChildAccountToken(mockChildAccount, mockChildAccountToken).as(
+        'switchAccount'
+      );
+
+      ui.drawer
+        .findByTitle('Switch Account')
+        .should('be.visible')
+        .within(() => {
+          cy.findByText(mockChildAccount.company).should('be.visible').click();
+        });
+
+      cy.wait('@switchAccount');
+
+      // Confirm that Cloud Manager updates local storage authentication values.
+      // Satisfy TypeScript using non-null assertions since we know what the mock data contains.
+      assertAuthLocalStorage(
+        mockChildAccountToken.token!,
+        mockChildAccountToken.expiry!,
+        mockChildAccountToken.scopes
+      );
+
+      // From this point forward, we will not have a valid test account token stored in local storage,
+      // so all non-intercepted API requests will respond with a 401 status code and we will get booted to login.
+      // We'll mitigate this by broadly mocking ALL API-v4 requests, then applying more specific mocks to the
+      // individual requests as needed.
+      mockAllApiRequests();
+      mockGetLinodes([]);
+      mockGetRegions([]);
+      mockGetEvents([]);
+      mockGetNotifications([]);
+
+      mockGetAccount(mockChildAccount);
+      mockGetProfile(mockParentProfile);
+      mockGetUser(mockParentUser);
+
+      // TODO Remove the call to `cy.reload()` once Cloud Manager automatically updates itself upon account switching.
+      // TODO Add assertions for toast upon account switch. This might involve improving mocks for events/notifications.
+      cy.reload();
+
+      // Confirm expected username and company are shown in user menu button.
+      assertUserMenuButton(
+        mockParentProfile.username,
+        mockChildAccount.company
+      );
+    });
+
+    /*
+     * - Confirms that Parent account user can switch to Child account using the user menu.
+     * - Confirms that Parent account information is initially displayed in user menu button.
+     * - Confirms that Child account information is displayed in user menu button after switch.
+     * - Confirms that Cloud updates local storage auth values upon account switch.
+     */
+    it('can switch from Parent account to Child account using user menu', () => {
+      mockGetProfile(mockParentProfile);
+      mockGetAccount(mockParentAccount);
+      mockGetChildAccounts([mockChildAccount]);
+      mockGetUser(mockParentUser);
+
+      cy.visitWithLogin('/');
+
+      // Confirm that Parent account username and company name are shown in user
+      // menu button, then click the button.
+      assertUserMenuButton(
+        mockParentProfile.username,
+        mockParentAccount.company
+      ).click();
+
+      // Click "Switch Account" button in user menu.
+      ui.userMenu
+        .find()
+        .should('be.visible')
+        .within(() => {
+          ui.button
+            .findByTitle('Switch Account')
+            .should('be.visible')
+            .should('be.enabled')
+            .click();
+        });
+
+      // Click mock company name in "Switch Account" drawer.
+      mockCreateChildAccountToken(mockChildAccount, mockChildAccountToken).as(
+        'switchAccount'
+      );
+
+      ui.drawer
+        .findByTitle('Switch Account')
+        .should('be.visible')
+        .within(() => {
+          cy.findByText(mockChildAccount.company).should('be.visible').click();
+        });
+
+      cy.wait('@switchAccount');
+
+      // Confirm that Cloud Manager updates local storage authentication values.
+      // Satisfy TypeScript using non-null assertions since we know what the mock data contains.
+      assertAuthLocalStorage(
+        mockChildAccountToken.token!,
+        mockChildAccountToken.expiry!,
+        mockChildAccountToken.scopes
+      );
+
+      // From this point forward, we will not have a valid test account token stored in local storage,
+      // so all non-intercepted API requests will respond with a 401 status code and we will get booted to login.
+      // We'll mitigate this by broadly mocking ALL API-v4 requests, then applying more specific mocks to the
+      // individual requests as needed.
+      mockAllApiRequests();
+      mockGetLinodes([]);
+      mockGetRegions([]);
+      mockGetEvents([]);
+      mockGetNotifications([]);
+      mockGetAccount(mockChildAccount);
+      mockGetProfile(mockParentProfile);
+      mockGetUser(mockParentUser);
+
+      // TODO Remove the call to `cy.reload()` once Cloud Manager automatically updates itself upon account switching.
+      // TODO Add assertions for toast upon account switch. This might involve improving mocks for events/notifications.
+      cy.reload();
+
+      // Confirm expected username and company are shown in user menu button.
+      assertUserMenuButton(
+        mockParentProfile.username,
+        mockChildAccount.company
+      );
+    });
+  });
+
+  /*
+   * Tests to confirm that Cloud handles account switching errors gracefully.
+   */
+  describe('Error flows', () => {
+    /*
+     * - Confirms error handling upon failure to fetch child accounts.
+     * - Confirms "Try Again" button can be used to re-fetch child accounts successfully.
+     * - Confirms error handling upon failure to create child account token.
+     */
+    it('handles account switching API errors', () => {
+      mockGetProfile(mockParentProfile);
+      mockGetAccount(mockParentAccount);
+      mockGetChildAccountsError('An unknown error has occurred', 500);
+      mockGetUser(mockParentUser);
+
+      cy.visitWithLogin('/account/billing');
+      ui.button
+        .findByTitle('Switch Account')
+        .should('be.visible')
+        .should('be.enabled')
+        .click();
+
+      ui.drawer
+        .findByTitle('Switch Account')
+        .should('be.visible')
+        .within(() => {
+          // Confirm error message upon failure to fetch child accounts.
+          cy.findByText('Unable to load data.').should('be.visible');
+          cy.findByText(
+            'Try again or contact support if the issue persists.'
+          ).should('be.visible');
+
+          // Click "Try Again" button and mock a successful response.
+          mockGetChildAccounts([mockChildAccount]);
+          ui.button
+            .findByTitle('Try again')
+            .should('be.visible')
+            .should('be.enabled')
+            .click();
+
+          // Click child company and mock an error.
+          // Confirm that Cloud Manager displays the error message in the drawer.
+          mockCreateChildAccountTokenError(mockChildAccount, mockErrorMessage);
+          cy.findByText(mockChildAccount.company).click();
+          cy.findByText(mockErrorMessage).should('be.visible');
+        });
+    });
+  });
+});
diff --git a/packages/manager/cypress/support/intercepts/account.ts b/packages/manager/cypress/support/intercepts/account.ts
index 5eb29242169..27838a71068 100644
--- a/packages/manager/cypress/support/intercepts/account.ts
+++ b/packages/manager/cypress/support/intercepts/account.ts
@@ -20,6 +20,7 @@ import type {
   InvoiceItem,
   Payment,
   PaymentMethod,
+  Token,
   User,
 } from '@linode/api-v4';
 
@@ -503,6 +504,7 @@ export const mockCancelAccountError = (
 /**
  * Intercepts GET request to fetch the account agreements and mocks the response.
  *
+ * @param agreements - Agreements with which to mock response.
  *
  * @returns Cypress chainable.
  */
@@ -516,9 +518,86 @@ export const mockGetAccountAgreements = (
   );
 };
 
+/**
+ * Intercepts GET request to fetch child accounts and mocks the response.
+ *
+ * @param childAccounts - Child account objects with which to mock response.
+ *
+ * @returns Cypress chainable.
+ */
+export const mockGetChildAccounts = (
+  childAccounts: Account[]
+): Cypress.Chainable<null> => {
+  return cy.intercept(
+    'GET',
+    apiMatcher('account/child-accounts*'),
+    paginateResponse(childAccounts)
+  );
+};
+
+/**
+ * Intercepts GET request to fetch child accounts and mocks an error response.
+ *
+ * @param errorMessage - API error message with which to mock response.
+ * @param statusCode - HTTP status code with which to mock response.
+ *
+ * @returns Cypress chainable.
+ */
+export const mockGetChildAccountsError = (
+  errorMessage: string = 'An unknown error has occurred',
+  statusCode: number = 500
+) => {
+  return cy.intercept(
+    'GET',
+    apiMatcher('account/child-accounts*'),
+    makeErrorResponse(errorMessage, statusCode)
+  );
+};
+
+/**
+ * Intercepts POST request to create a child account token and mocks the response.
+ *
+ * @param childAccount - Child account for which to create a token.
+ * @param childAccountToken - Token object with which to mock response.
+ *
+ * @returns Cypress chainable.
+ */
+export const mockCreateChildAccountToken = (
+  childAccount: Account,
+  childAccountToken: Token
+): Cypress.Chainable<null> => {
+  return cy.intercept(
+    'POST',
+    apiMatcher(`account/child-accounts/${childAccount.euuid}/token`),
+    makeResponse(childAccountToken)
+  );
+};
+
+/**
+ * Intercepts POST request to create a child account token and mocks error response.
+ *
+ * @param childAccount - Child account for which to mock error response.
+ * @param errorMessage - API error message with which to mock response.
+ * @param statusCode - HTTP status code with which to mock response.
+ *
+ * @returns Cypress chainable.
+ */
+export const mockCreateChildAccountTokenError = (
+  childAccount: Account,
+  errorMessage: string = 'An unknown error has occurred',
+  statusCode: number = 500
+): Cypress.Chainable<null> => {
+  return cy.intercept(
+    'POST',
+    apiMatcher(`account/child-accounts/${childAccount.euuid}/token`),
+    makeErrorResponse(errorMessage, statusCode)
+  );
+};
+
 /**
  * Intercepts GET request to fetch the account logins and mocks the response.
  *
+ * @param accountLogins - Account login objects with which to mock response.
  *
  * @returns Cypress chainable.
  */
diff --git a/packages/manager/cypress/support/intercepts/events.ts b/packages/manager/cypress/support/intercepts/events.ts
index 2ae3685bd5e..eea7b5fac12 100644
--- a/packages/manager/cypress/support/intercepts/events.ts
+++ b/packages/manager/cypress/support/intercepts/events.ts
@@ -2,7 +2,7 @@
  * @file Mocks and intercepts related to notification and event handling.
  */
 
-import { Event } from '@linode/api-v4';
+import type { Event, Notification } from '@linode/api-v4';
 import { apiMatcher } from 'support/util/intercepts';
 import { paginateResponse } from 'support/util/paginate';
 
@@ -20,3 +20,20 @@ export const mockGetEvents = (events: Event[]): Cypress.Chainable => {
     paginateResponse(events)
   );
 };
+
+/**
+ * Intercepts GET request to fetch notifications and mocks response.
+ *
+ * @param notifications - Notifications with which to mock response.
+ *
+ * @returns Cypress chainable.
+ */
+export const mockGetNotifications = (
+  notifications: Notification[]
+): Cypress.Chainable => {
+  return cy.intercept(
+    'GET',
+    apiMatcher('account/notifications*'),
+    paginateResponse(notifications)
+  );
+};
diff --git a/packages/manager/cypress/support/intercepts/general.ts b/packages/manager/cypress/support/intercepts/general.ts
index 3cd13083bc5..09cd74e0167 100644
--- a/packages/manager/cypress/support/intercepts/general.ts
+++ b/packages/manager/cypress/support/intercepts/general.ts
@@ -2,6 +2,25 @@ import { makeErrorResponse } from 'support/util/errors';
 import { apiMatcher } from 'support/util/intercepts';
 import { makeResponse } from 'support/util/response';
 
+/**
+ * Intercepts all requests to Linode API v4 and mocks an HTTP response.
+ *
+ * This is useful to apply a baseline mock on all Linode API v4 requests, e.g.
+ * to prevent 401 responses. More fine-grained mocking can be set up with
+ * subsequent calls to other mock utils.
+ *
+ * @param body - Body data with which to mock response.
+ * @param statusCode - HTTP status code with which to mock response.
+ *
+ * @returns Cypress chainable.
+ */
+export const mockAllApiRequests = (
+  body: any = {},
+  statusCode: number = 200
+) => {
+  return cy.intercept(apiMatcher('**/*'), makeResponse(body, statusCode));
+};
+
 /**
  * Intercepts GET request to given URL and mocks an HTTP 200 response with the given content.
  *
diff --git a/packages/manager/cypress/support/util/local-storage.ts b/packages/manager/cypress/support/util/local-storage.ts
new file mode 100644
index 00000000000..db748cb4105
--- /dev/null
+++ b/packages/manager/cypress/support/util/local-storage.ts
@@ -0,0 +1,30 @@
+/**
+ * @file Utilities to access and validate Local Storage data.
+ */
+
+/**
+ * Asserts that a local storage item has a given value.
+ *
+ * @param key - Local storage item key.
+ * @param value - Local storage item value to assert.
+ */
+export const assertLocalStorageValue = (key: string, value: any) => {
+  cy.getAllLocalStorage().then((localStorageData: any) => {
+    const origin = Cypress.config('baseUrl');
+    if (!origin) {
+      // This should never happen in practice.
+      throw new Error('Unable to retrieve Cypress base URL configuration');
+    }
+    if (!localStorageData[origin]) {
+      throw new Error(
+        `Unable to retrieve local storage data from origin '${origin}'`
+      );
+    }
+    if (!localStorageData[origin][key]) {
+      throw new Error(
+        `No local storage data exists for key '${key}' and origin '${origin}'`
+      );
+    }
+    expect(localStorageData[origin][key]).equals(value);
+  });
+};