diff --git a/keyserver/src/endpoints.js b/keyserver/src/endpoints.js
--- a/keyserver/src/endpoints.js
+++ b/keyserver/src/endpoints.js
@@ -41,6 +41,7 @@
   threadLeaveResponder,
   threadUpdateResponder,
   threadCreationResponder,
+  threadFetchMediaResponder,
   threadJoinResponder,
 } from './responders/thread-responders.js';
 import {
@@ -133,6 +134,10 @@
     responder: messageFetchResponder,
     requiredPolicies: baseLegalPolicies,
   },
+  fetch_thread_media: {
+    responder: threadFetchMediaResponder,
+    requiredPolicies: baseLegalPolicies,
+  },
   get_session_public_keys: {
     responder: getSessionPublicKeysResponder,
     requiredPolicies: baseLegalPolicies,
diff --git a/keyserver/src/fetchers/upload-fetchers.js b/keyserver/src/fetchers/upload-fetchers.js
--- a/keyserver/src/fetchers/upload-fetchers.js
+++ b/keyserver/src/fetchers/upload-fetchers.js
@@ -5,6 +5,10 @@
 import type { Media } from 'lib/types/media-types.js';
 import type { MediaMessageServerDBContent } from 'lib/types/messages/media.js';
 import { getUploadIDsFromMediaMessageServerDBContents } from 'lib/types/messages/media.js';
+import type {
+  ThreadFetchMediaResult,
+  ThreadFetchMediaRequest,
+} from 'lib/types/thread-types.js';
 import { ServerError } from 'lib/utils/errors.js';
 
 import { dbQuery, SQL } from '../database/database.js';
@@ -116,7 +120,9 @@
   return result.map(mediaFromRow);
 }
 
-async function fetchMediaForThread(request: any): Promise<any> {
+async function fetchMediaForThread(
+  request: ThreadFetchMediaRequest,
+): Promise<ThreadFetchMediaResult> {
   // Fetch the uploads used for the uploadsMap containing the thread media
   const query = SQL`
     SELECT id AS uploadID, secret AS uploadSecret,
diff --git a/keyserver/src/responders/thread-responders.js b/keyserver/src/responders/thread-responders.js
--- a/keyserver/src/responders/thread-responders.js
+++ b/keyserver/src/responders/thread-responders.js
@@ -15,6 +15,8 @@
   type NewThreadResponse,
   type ServerThreadJoinRequest,
   type ThreadJoinResult,
+  type ThreadFetchMediaResult,
+  type ThreadFetchMediaRequest,
   threadTypes,
 } from 'lib/types/thread-types.js';
 import { values } from 'lib/utils/objects.js';
@@ -31,6 +33,7 @@
 } from './entry-responders.js';
 import { createThread } from '../creators/thread-creator.js';
 import { deleteThread } from '../deleters/thread-deleters.js';
+import { fetchMediaForThread } from '../fetchers/upload-fetchers.js';
 import type { Viewer } from '../session/viewer.js';
 import {
   updateRole,
@@ -176,6 +179,21 @@
   return await joinThread(viewer, request);
 }
 
+const threadFetchMediaRequestInputValidator = tShape({
+  threadID: t.String,
+  limit: t.Number,
+  offset: t.Number,
+  currentMediaIDs: t.list(t.String),
+});
+async function threadFetchMediaResponder(
+  viewer: Viewer,
+  input: any,
+): Promise<ThreadFetchMediaResult> {
+  const request: ThreadFetchMediaRequest = input;
+  await validateInput(viewer, threadFetchMediaRequestInputValidator, request);
+  return await fetchMediaForThread(request);
+}
+
 export {
   threadDeletionResponder,
   roleUpdateResponder,
@@ -184,5 +202,6 @@
   threadUpdateResponder,
   threadCreationResponder,
   threadJoinResponder,
+  threadFetchMediaResponder,
   newThreadRequestInputValidator,
 };
diff --git a/lib/actions/thread-actions.js b/lib/actions/thread-actions.js
--- a/lib/actions/thread-actions.js
+++ b/lib/actions/thread-actions.js
@@ -10,6 +10,8 @@
   NewThreadResult,
   ClientThreadJoinRequest,
   ThreadJoinPayload,
+  ThreadFetchMediaRequest,
+  ThreadFetchMediaResult,
 } from '../types/thread-types.js';
 import type { CallServerEndpoint } from '../utils/call-server-endpoint.js';
 import { values } from '../utils/objects.js';
@@ -162,6 +164,15 @@
   };
 };
 
+const fetchThreadMedia = (
+  callServerEndpoint: CallServerEndpoint,
+): ((
+  request: ThreadFetchMediaRequest,
+) => Promise<ThreadFetchMediaResult>) => async request => {
+  const response = await callServerEndpoint('fetch_thread_media', request);
+  return response;
+};
+
 export {
   deleteThreadActionTypes,
   deleteThread,
@@ -177,4 +188,5 @@
   joinThread,
   leaveThreadActionTypes,
   leaveThread,
+  fetchThreadMedia,
 };
diff --git a/lib/types/endpoints.js b/lib/types/endpoints.js
--- a/lib/types/endpoints.js
+++ b/lib/types/endpoints.js
@@ -61,6 +61,7 @@
   FETCH_ENTRY_REVISIONS: 'fetch_entry_revisions',
   FETCH_ERROR_REPORT_INFOS: 'fetch_error_report_infos',
   FETCH_MESSAGES: 'fetch_messages',
+  FETCH_THREAD_MEDIA: 'fetch_thread_media',
   GET_SESSION_PUBLIC_KEYS: 'get_session_public_keys',
   JOIN_THREAD: 'join_thread',
   LEAVE_THREAD: 'leave_thread',
diff --git a/lib/types/thread-types.js b/lib/types/thread-types.js
--- a/lib/types/thread-types.js
+++ b/lib/types/thread-types.js
@@ -4,6 +4,7 @@
 
 import type { Shape } from './core.js';
 import type { CalendarQuery, RawEntryInfo } from './entry-types.js';
+import type { Media } from './media-types.js';
 import type {
   RawMessageInfo,
   MessageTruncationStatuses,
@@ -453,6 +454,17 @@
   +userInfos: $ReadOnlyArray<UserInfo>,
 };
 
+export type ThreadFetchMediaResult = {
+  +media: $ReadOnlyArray<Media>,
+  +adjustedOffset: number,
+};
+export type ThreadFetchMediaRequest = {
+  +threadID: string,
+  +limit: number,
+  +offset: number,
+  +currentMediaIDs: $ReadOnlyArray<string>,
+};
+
 export type SidebarInfo = {
   +threadInfo: ThreadInfo,
   +lastUpdatedTime: number,