diff --git a/lib/hooks/thread-hooks.js b/lib/hooks/thread-hooks.js
--- a/lib/hooks/thread-hooks.js
+++ b/lib/hooks/thread-hooks.js
@@ -20,7 +20,9 @@
   useFetchFarcasterConversation,
   useFetchFarcasterMessages,
   useUpdateFarcasterGroupNameAndDescription,
+  useModifyFarcasterMembershipInput,
 } from '../shared/farcaster/farcaster-api.js';
+import { useFetchConversation } from '../shared/farcaster/farcaster-hooks.js';
 import { threadSpecs } from '../shared/threads/thread-specs.js';
 import { permissionsAndAuthRelatedRequestTimeout } from '../shared/timeouts.js';
 import type {
@@ -349,6 +351,9 @@
 ) => Promise<ChangeThreadSettingsPayload> {
   const keyserverCall = useKeyserverCall(changeThreadMemberRoles);
   const dispatchActionPromise = useDispatchActionPromise();
+  const modifyFarcasterMembership = useModifyFarcasterMembershipInput();
+  const fetchConversation = useFetchConversation();
+  const auxUserStore = useSelector(state => state.auxUserStore);
   return React.useCallback(
     async (input: ChangeThreadMemberRolesInput) => {
       const { threadInfo, memberIDs, newRole } = input;
@@ -367,10 +372,19 @@
         {
           keyserverCall,
           dispatchActionPromise,
+          modifyFarcasterMembership,
+          fetchConversation,
+          auxUserStore,
         },
       );
     },
-    [dispatchActionPromise, keyserverCall],
+    [
+      dispatchActionPromise,
+      keyserverCall,
+      modifyFarcasterMembership,
+      fetchConversation,
+      auxUserStore,
+    ],
   );
 }
 
diff --git a/lib/shared/farcaster/farcaster-api.js b/lib/shared/farcaster/farcaster-api.js
--- a/lib/shared/farcaster/farcaster-api.js
+++ b/lib/shared/farcaster/farcaster-api.js
@@ -492,6 +492,55 @@
   );
 }
 
+export type ModifyFarcasterMembershipInput =
+  | {
+      +conversationId: string,
+      +action: 'demote',
+      +targetFid: number,
+    }
+  | {
+      +conversationId: string,
+      +action: 'promote',
+      +targetFid: number,
+    }
+  | {
+      +conversationId: string,
+      +action: 'remove',
+      +targetFid: number,
+    }
+  | {
+      +conversationId: string,
+      +action: 'add',
+      +inviteCode: string,
+    }
+  | {
+      +conversationId: string,
+      +action: 'add',
+      +targetFid: number,
+    }
+  | {
+      +conversationId: string,
+      +action: 'add',
+      +targetFids: $ReadOnlyArray<number>,
+    };
+
+function useModifyFarcasterMembershipInput(): (
+  input: ModifyFarcasterMembershipInput,
+) => Promise<void> {
+  const { sendFarcasterRequest } = useTunnelbroker();
+  return React.useCallback(
+    async (input: ModifyFarcasterMembershipInput) => {
+      await sendFarcasterRequest({
+        apiVersion: 'v2',
+        endpoint: 'direct-cast-group-membership',
+        method: { type: 'POST' },
+        payload: JSON.stringify(input),
+      });
+    },
+    [sendFarcasterRequest],
+  );
+}
+
 export {
   useSendFarcasterTextMessage,
   useFetchFarcasterMessages,
@@ -503,4 +552,5 @@
   useMarkFarcasterDirectCastUnread,
   useCreateFarcasterGroup,
   useGetFarcasterDirectCastUsers,
+  useModifyFarcasterMembershipInput,
 };
diff --git a/lib/shared/threads/protocols/farcaster-thread-protocol.js b/lib/shared/threads/protocols/farcaster-thread-protocol.js
--- a/lib/shared/threads/protocols/farcaster-thread-protocol.js
+++ b/lib/shared/threads/protocols/farcaster-thread-protocol.js
@@ -3,6 +3,7 @@
 import invariant from 'invariant';
 
 import { fetchMessagesBeforeCursorActionTypes } from '../../../actions/message-actions.js';
+import { changeThreadMemberRolesActionTypes } from '../../../actions/thread-action-types.js';
 import { getFarcasterRolePermissionsBlobs } from '../../../permissions/farcaster-permissions.js';
 import type { RolePermissionBlobs } from '../../../permissions/thread-permissions.js';
 import type { SetThreadUnreadStatusPayload } from '../../../types/activity-types.js';
@@ -45,6 +46,7 @@
 import { createFarcasterRawThreadInfo } from '../../../utils/create-farcaster-raw-thread-info.js';
 import { farcasterThreadIDRegExp } from '../../../utils/validation-utils.js';
 import { generatePendingThreadColor } from '../../color-utils.js';
+import { type ModifyFarcasterMembershipInput } from '../../farcaster/farcaster-api.js';
 import { farcasterMessageValidator } from '../../farcaster/farcaster-messages-types.js';
 import {
   conversationIDFromFarcasterThreadID,
@@ -58,6 +60,7 @@
   getSingleOtherUser,
   threadIsPending,
   threadOtherMembers,
+  roleIsAdminRole,
 } from '../../thread-utils.js';
 import type {
   ChangeThreadSettingsUtils,
@@ -75,6 +78,8 @@
   UpdateSubscriptionUtils,
   ProtocolCreatePendingThreadInput,
   CreateRealThreadParameters,
+  ProtocolChangeThreadMemberRolesInput,
+  ChangeThreadMemberRolesUtils,
 } from '../thread-spec.js';
 
 const farcasterThreadProtocol: ThreadProtocol<MemberInfoSansPermissions> = {
@@ -277,6 +282,67 @@
     throw new Error('addThreadMembers method is not yet implemented');
   },
 
+  changeThreadMemberRoles: async (
+    input: ProtocolChangeThreadMemberRolesInput,
+    utils: ChangeThreadMemberRolesUtils,
+  ): Promise<ChangeThreadSettingsPayload> => {
+    const { threadInfo, memberIDs, newRole } = input;
+    const {
+      modifyFarcasterMembership,
+      fetchConversation,
+      dispatchActionPromise,
+      auxUserStore,
+    } = utils;
+
+    const conversationId = conversationIDFromFarcasterThreadID(threadInfo.id);
+
+    // Determine if we're promoting or demoting based on role
+    const isPromoting = roleIsAdminRole(threadInfo.roles[newRole]);
+
+    const promise = (async () => {
+      const membershipPromises = memberIDs
+        .map(memberID => {
+          const targetFid =
+            auxUserStore.auxUserInfos[memberID]?.fid ??
+            extractFIDFromUserID(memberID);
+          if (targetFid) {
+            let modifyFarcasterMembershipInput: ModifyFarcasterMembershipInput =
+              {
+                conversationId,
+                action: 'demote',
+                targetFid: parseInt(targetFid, 10),
+              };
+
+            if (isPromoting) {
+              modifyFarcasterMembershipInput = {
+                conversationId,
+                action: 'promote',
+                targetFid: parseInt(targetFid, 10),
+              };
+            }
+
+            return modifyFarcasterMembership(modifyFarcasterMembershipInput);
+          }
+          return null;
+        })
+        .filter(Boolean);
+
+      await Promise.all(membershipPromises);
+
+      await fetchConversation(conversationId);
+
+      return {
+        threadID: threadInfo.id,
+        updatesResult: { newUpdates: [] },
+        newMessageInfos: [],
+      };
+    })();
+
+    void dispatchActionPromise(changeThreadMemberRolesActionTypes, promise);
+
+    return await promise;
+  },
+
   updateSubscription: async (
     protocolInput: ProtocolUpdateSubscriptionInput,
     utils: UpdateSubscriptionUtils,
diff --git a/lib/shared/threads/thread-spec.js b/lib/shared/threads/thread-spec.js
--- a/lib/shared/threads/thread-spec.js
+++ b/lib/shared/threads/thread-spec.js
@@ -99,6 +99,7 @@
   MarkFarcasterDirectCastUnreadInput,
   CreateFarcasterGroupResult,
   CreateFarcasterGroupInput,
+  ModifyFarcasterMembershipInput,
 } from '../farcaster/farcaster-api.js';
 import type { FarcasterConversation } from '../farcaster/farcaster-conversation-types.js';
 import type { FetchMessagesFromDBType } from '../message-utils.js';
@@ -246,6 +247,11 @@
 export type ChangeThreadMemberRolesUtils = {
   +keyserverCall: ProtocolChangeThreadMemberRolesInput => Promise<ChangeThreadSettingsPayload>,
   +dispatchActionPromise: DispatchActionPromise,
+  +modifyFarcasterMembership: (
+    input: ModifyFarcasterMembershipInput,
+  ) => Promise<void>,
+  +fetchConversation: (conversationId: string) => Promise<mixed>,
+  +auxUserStore: AuxUserStore,
 };
 
 export type ProtocolUpdateSubscriptionInput = {