diff --git a/.github/ISSUE_TEMPLATE/bug_report.yml b/.github/ISSUE_TEMPLATE/bug_report.yml
index a52afb389..4aacdee6b 100644
--- a/.github/ISSUE_TEMPLATE/bug_report.yml
+++ b/.github/ISSUE_TEMPLATE/bug_report.yml
@@ -96,6 +96,7 @@ body:
         - Message
         - Reaction
         - GuildScheduledEvent
+        - ThreadMember
       multiple: true
     validations:
       required: true
diff --git a/packages/discord.js/src/client/actions/Action.js b/packages/discord.js/src/client/actions/Action.js
index f70d3ca70..7f0553012 100644
--- a/packages/discord.js/src/client/actions/Action.js
+++ b/packages/discord.js/src/client/actions/Action.js
@@ -110,6 +110,10 @@ class GenericAction {
       Partials.GuildScheduledEvent,
     );
   }
+
+  getThreadMember(id, manager) {
+    return this.getPayload({ user_id: id }, manager, id, Partials.ThreadMember, false);
+  }
 }
 
 module.exports = GenericAction;
diff --git a/packages/discord.js/src/client/actions/ThreadMembersUpdate.js b/packages/discord.js/src/client/actions/ThreadMembersUpdate.js
index 26ab70efb..6f7f0a4ff 100644
--- a/packages/discord.js/src/client/actions/ThreadMembersUpdate.js
+++ b/packages/discord.js/src/client/actions/ThreadMembersUpdate.js
@@ -1,5 +1,6 @@
 'use strict';
 
+const { Collection } = require('@discordjs/collection');
 const Action = require('./Action');
 const Events = require('../../util/Events');
 
@@ -8,24 +9,35 @@ class ThreadMembersUpdateAction extends Action {
     const client = this.client;
     const thread = client.channels.cache.get(data.id);
     if (thread) {
-      const old = thread.members.cache.clone();
       thread.memberCount = data.member_count;
+      const addedMembers = new Collection();
+      const removedMembers = new Collection();
 
-      data.added_members?.forEach(rawMember => {
-        thread.members._add(rawMember);
-      });
+      data.added_members?.reduce(
+        (_addedMembers, addedMember) => _addedMembers.set(addedMember.user_id, thread.members._add(addedMember)),
+        addedMembers,
+      );
 
-      data.removed_member_ids?.forEach(memberId => {
-        thread.members.cache.delete(memberId);
-      });
+      data.removed_member_ids?.reduce((removedMembersIds, removedMembersId) => {
+        const threadMember = this.getThreadMember(removedMembersId, thread.members);
+        if (threadMember) removedMembersIds.set(threadMember.id, threadMember);
+        thread.members.cache.delete(removedMembersId);
+        return removedMembersIds;
+      }, removedMembers);
+
+      if (addedMembers.size === 0 && removedMembers.size === 0) {
+        // Uncached thread member(s) left.
+        return {};
+      }
 
       /**
        * Emitted whenever members are added or removed from a thread. Requires `GUILD_MEMBERS` privileged intent
        * @event Client#threadMembersUpdate
-       * @param {Collection<Snowflake, ThreadMember>} oldMembers The members before the update
-       * @param {Collection<Snowflake, ThreadMember>} newMembers The members after the update
+       * @param {ThreadChannel} thread The thread where members got updated
+       * @param {Collection<Snowflake, ThreadMember>} addedMembers The members that were added
+       * @param {Collection<Snowflake, ThreadMember>} removedMembers The members that were removed
        */
-      client.emit(Events.ThreadMembersUpdate, old, thread.members.cache);
+      client.emit(Events.ThreadMembersUpdate, thread, addedMembers, removedMembers);
     }
     return {};
   }
diff --git a/packages/discord.js/src/structures/ThreadMember.js b/packages/discord.js/src/structures/ThreadMember.js
index 9da8677d0..2b6743a93 100644
--- a/packages/discord.js/src/structures/ThreadMember.js
+++ b/packages/discord.js/src/structures/ThreadMember.js
@@ -23,6 +23,12 @@ class ThreadMember extends Base {
      */
     this.joinedTimestamp = null;
 
+    /**
+     * The flags for this thread member. This will be `null` if partial.
+     * @type {?ThreadMemberFlagsBitField}
+     */
+    this.flags = null;
+
     /**
      * The id of the thread member
      * @type {Snowflake}
@@ -34,14 +40,16 @@ class ThreadMember extends Base {
 
   _patch(data) {
     if ('join_timestamp' in data) this.joinedTimestamp = Date.parse(data.join_timestamp);
+    if ('flags' in data) this.flags = new ThreadMemberFlagsBitField(data.flags).freeze();
+  }
 
-    if ('flags' in data) {
-      /**
-       * The flags for this thread member
-       * @type {ThreadMemberFlagsBitField}
-       */
-      this.flags = new ThreadMemberFlagsBitField(data.flags).freeze();
-    }
+  /**
+   * Whether this thread member is a partial
+   * @type {boolean}
+   * @readonly
+   */
+  get partial() {
+    return this.flags === null;
   }
 
   /**
diff --git a/packages/discord.js/src/util/Partials.js b/packages/discord.js/src/util/Partials.js
index 7bbe517d3..0429b2327 100644
--- a/packages/discord.js/src/util/Partials.js
+++ b/packages/discord.js/src/util/Partials.js
@@ -2,4 +2,12 @@
 
 const { createEnum } = require('./Enums');
 
-module.exports = createEnum(['User', 'Channel', 'GuildMember', 'Message', 'Reaction', 'GuildScheduledEvent']);
+module.exports = createEnum([
+  'User',
+  'Channel',
+  'GuildMember',
+  'Message',
+  'Reaction',
+  'GuildScheduledEvent',
+  'ThreadMember',
+]);
diff --git a/packages/discord.js/typings/index.d.ts b/packages/discord.js/typings/index.d.ts
index 82a92a5a4..30ab2a843 100644
--- a/packages/discord.js/typings/index.d.ts
+++ b/packages/discord.js/typings/index.d.ts
@@ -2338,6 +2338,7 @@ export class ThreadMember extends Base {
   public get manageable(): boolean;
   public thread: ThreadChannel;
   public get user(): User | null;
+  public get partial(): false;
   public remove(reason?: string): Promise<ThreadMember>;
 }
 
@@ -3289,7 +3290,7 @@ export interface AddGuildMemberOptions {
   fetchWhenExisting?: boolean;
 }
 
-export type AllowedPartial = User | Channel | GuildMember | Message | MessageReaction;
+export type AllowedPartial = User | Channel | GuildMember | Message | MessageReaction | ThreadMember;
 
 export type AllowedThreadTypeForNewsChannel = ChannelType.GuildNewsThread;
 
@@ -3671,8 +3672,9 @@ export interface ClientEvents {
   threadListSync: [threads: Collection<Snowflake, ThreadChannel>];
   threadMemberUpdate: [oldMember: ThreadMember, newMember: ThreadMember];
   threadMembersUpdate: [
-    oldMembers: Collection<Snowflake, ThreadMember>,
-    newMembers: Collection<Snowflake, ThreadMember>,
+    thread: ThreadChannel,
+    addedMembers: Collection<Snowflake, ThreadMember>,
+    removedMembers: Collection<Snowflake, ThreadMember | PartialThreadMember>,
   ];
   threadUpdate: [oldThread: ThreadChannel, newThread: ThreadChannel];
   typingStart: [typing: Typing];
@@ -4877,6 +4879,8 @@ export interface PartialMessage
 
 export interface PartialMessageReaction extends Partialize<MessageReaction, 'count'> {}
 
+export interface PartialThreadMember extends Partialize<ThreadMember, 'flags' | 'joinedAt' | 'joinedTimestamp'> {}
+
 export interface PartialOverwriteData {
   id: Snowflake | number;
   type?: OverwriteType;
@@ -4895,6 +4899,7 @@ export enum Partials {
   Message,
   Reaction,
   GuildScheduledEvent,
+  ThreadMember,
 }
 
 export interface PartialUser extends Partialize<User, 'username' | 'tag' | 'discriminator'> {}
diff --git a/packages/discord.js/typings/index.test-d.ts b/packages/discord.js/typings/index.test-d.ts
index d1fe99a1a..892acf532 100644
--- a/packages/discord.js/typings/index.test-d.ts
+++ b/packages/discord.js/typings/index.test-d.ts
@@ -107,6 +107,8 @@ import {
   CategoryChannelChildManager,
   ActionRowData,
   MessageActionRowComponentData,
+  PartialThreadMember,
+  ThreadMemberFlagsBitField,
   Embed,
 } from '.';
 import { expectAssignable, expectDeprecated, expectNotAssignable, expectNotType, expectType } from 'tsd';
@@ -719,6 +721,22 @@ client.on('messageCreate', async message => {
   });
 });
 
+client.on('threadMembersUpdate', (thread, addedMembers, removedMembers) => {
+  expectType<ThreadChannel>(thread);
+  expectType<Collection<Snowflake, ThreadMember>>(addedMembers);
+  expectType<Collection<Snowflake, ThreadMember | PartialThreadMember>>(removedMembers);
+  const left = removedMembers.first();
+  if (!left) return;
+
+  if (left.partial) {
+    expectType<PartialThreadMember>(left);
+    expectType<null>(left.flags);
+  } else {
+    expectType<ThreadMember>(left);
+    expectType<ThreadMemberFlagsBitField>(left.flags);
+  }
+});
+
 client.on('interactionCreate', async interaction => {
   expectType<Snowflake | null>(interaction.guildId);
   expectType<Snowflake | null>(interaction.channelId);