diff --git a/src/server/api/endpoints/users/list/push.ts b/src/server/api/endpoints/users/list/push.ts
index e69de29bb..f21234775 100644
--- a/src/server/api/endpoints/users/list/push.ts
+++ b/src/server/api/endpoints/users/list/push.ts
@@ -0,0 +1,48 @@
+import $ from 'cafy'; import ID from '../../../../../cafy-id';
+import UserList from '../../../../../models/user-list';
+import User from '../../../../../models/user';
+
+/**
+ * Add a user to a user list
+ */
+module.exports = async (params, me) => new Promise(async (res, rej) => {
+	// Get 'listId' parameter
+	const [listId, listIdErr] = $(params.listId).type(ID).$;
+	if (listIdErr) return rej('invalid listId param');
+
+	// Fetch the list
+	const userList = await UserList.findOne({
+		_id: listId,
+		userId: me._id,
+	});
+
+	if (userList == null) {
+		return rej('list not found');
+	}
+
+	// Get 'userId' parameter
+	const [userId, userIdErr] = $(params.userId).type(ID).$;
+	if (userIdErr) return rej('invalid userId param');
+
+	// Fetch the user
+	const user = await User.findOne({
+		_id: userId
+	});
+
+	if (user == null) {
+		return rej('user not found');
+	}
+
+	if (userList.userIds.map(id => id.toHexString()).includes(user._id.toHexString())) {
+		return rej('the user already added');
+	}
+
+	// Push the user
+	await UserList.update({ _id: userList._id }, {
+		$push: {
+			userIds: user._id
+		}
+	});
+
+	res();
+});