diff --git a/keyserver/src/deleters/thread-deleters.js b/keyserver/src/deleters/thread-deleters.js
--- a/keyserver/src/deleters/thread-deleters.js
+++ b/keyserver/src/deleters/thread-deleters.js
@@ -15,6 +15,7 @@
 import {
   fetchThreadInfos,
   fetchServerThreadInfos,
+  fetchContainedThreadIDs,
 } from '../fetchers/thread-fetchers.js';
 import { fetchThreadPermissionsBlob } from '../fetchers/thread-permission-fetchers.js';
 import { fetchUpdateInfoForThreadDeletion } from '../fetchers/update-fetchers.js';
@@ -30,11 +31,7 @@
   }
   const { threadID } = threadDeletionRequest;
 
-  const [permissionsBlob, { threadInfos: serverThreadInfos }] =
-    await Promise.all([
-      fetchThreadPermissionsBlob(viewer, threadID),
-      fetchServerThreadInfos(SQL`t.id = ${threadID}`),
-    ]);
+  const permissionsBlob = await fetchThreadPermissionsBlob(viewer, threadID);
 
   if (!permissionsBlob) {
     // This should only occur if the first request goes through but the client
@@ -60,14 +57,18 @@
     throw new ServerError('invalid_credentials');
   }
 
-  await rescindPushNotifs(
-    SQL`n.thread = ${threadID}`,
-    SQL`IF(m.thread = ${threadID}, NULL, m.thread)`,
-  );
-
-  // TODO: if org, delete all descendant threads as well. make sure to warn user
   // TODO: handle descendant thread permission update correctly.
   //       thread-permission-updaters should be used for descendant threads.
+  const threadIDs = await fetchContainedThreadIDs(threadID);
+
+  const [{ threadInfos: serverThreadInfos }] = await Promise.all([
+    fetchServerThreadInfos(SQL`t.id IN (${threadIDs})`),
+    rescindPushNotifs(
+      SQL`n.thread IN (${threadIDs})`,
+      SQL`IF(m.thread IN (${threadIDs}), NULL, m.thread)`,
+    ),
+  ]);
+
   const query = SQL`
     DELETE t, ic, d, id, e, ie, re, ire, mm, r, ir, ms, im, up, iu, f, n, ino
     FROM threads t
@@ -88,19 +89,20 @@
     LEFT JOIN focused f ON f.thread = t.id
     LEFT JOIN notifications n ON n.thread = t.id
     LEFT JOIN ids ino ON ino.id = n.id
-    WHERE t.id = ${threadID}
+    WHERE t.id IN (${threadIDs})
   `;
 
-  const serverThreadInfo = serverThreadInfos[threadID];
   const time = Date.now();
   const updateDatas = [];
-  for (const memberInfo of serverThreadInfo.members) {
-    updateDatas.push({
-      type: updateTypes.DELETE_THREAD,
-      userID: memberInfo.id,
-      time,
-      threadID,
-    });
+  for (const containedThreadID of threadIDs) {
+    for (const memberInfo of serverThreadInfos[containedThreadID].members) {
+      updateDatas.push({
+        type: updateTypes.DELETE_THREAD,
+        userID: memberInfo.id,
+        time,
+        threadID: containedThreadID,
+      });
+    }
   }
 
   const [{ viewerUpdates }] = await Promise.all([
diff --git a/keyserver/src/fetchers/thread-fetchers.js b/keyserver/src/fetchers/thread-fetchers.js
--- a/keyserver/src/fetchers/thread-fetchers.js
+++ b/keyserver/src/fetchers/thread-fetchers.js
@@ -308,6 +308,25 @@
   return threads.threadInfos[threadID];
 }
 
+async function fetchContainedThreadIDs(
+  parentThreadID: string,
+): Promise<Array<string>> {
+  const query = SQL`
+    WITH RECURSIVE thread_tree AS (
+      SELECT id, containing_thread_id
+      FROM threads
+      WHERE id = ${parentThreadID}
+      UNION ALL
+      SELECT t.id, t.containing_thread_id
+      FROM threads t
+      JOIN thread_tree tt ON t.containing_thread_id = tt.id
+    )
+    SELECT id FROM thread_tree
+  `;
+  const [result] = await dbQuery(query);
+  return result.map(row => row.id.toString());
+}
+
 export {
   fetchServerThreadInfos,
   fetchThreadInfos,
@@ -318,4 +337,5 @@
   personalThreadQuery,
   fetchPersonalThreadID,
   serverThreadInfoFromMessageInfo,
+  fetchContainedThreadIDs,
 };