diff --git a/shared/viewmodels/RoomDirectoryViewModel.js b/shared/viewmodels/RoomDirectoryViewModel.js
index 1b28022..0014ac1 100644
--- a/shared/viewmodels/RoomDirectoryViewModel.js
+++ b/shared/viewmodels/RoomDirectoryViewModel.js
@@ -88,9 +88,15 @@ class RoomDirectoryViewModel extends ViewModel {
       );
     });
     this._roomCardViewModelsFilterMap = new ApplyMap(this._roomCardViewModelsMap);
-    this._roomCardViewModels = this._roomCardViewModelsFilterMap.sortValues((/*a, b*/) => {
-      // Sort doesn't matter
-      return 1;
+    this._roomCardViewModels = this._roomCardViewModelsFilterMap.sortValues((a, b) => {
+      // Sort by the number of joined members descending (highest to lowest)
+      if (b.numJoinedMembers > a.numJoinedMembers) {
+        return 1;
+      } else if (b.numJoinedMembers < a.numJoinedMembers) {
+        return -1;
+      }
+
+      return 0;
     });
 
     this._safeSearchEnabled = true;