diff --git a/src/applications/maniphest/controller/ManiphestTaskEditController.php b/src/applications/maniphest/controller/ManiphestTaskEditController.php
--- a/src/applications/maniphest/controller/ManiphestTaskEditController.php
+++ b/src/applications/maniphest/controller/ManiphestTaskEditController.php
@@ -383,6 +383,17 @@
                 return new Aphront404Response();
               }
 
+              // re-load projects for accuracy as they are not re-loaded via
+              // the editor
+              $project_phids = PhabricatorEdgeQuery::loadDestinationPHIDs(
+                $task->getPHID(),
+                PhabricatorProjectObjectHasProjectEdgeType::EDGECONST);
+              $task->attachProjectPHIDs($project_phids);
+              $remove_from_board = false;
+              if (!in_array($column->getProjectPHID(), $project_phids)) {
+                $remove_from_board = true;
+              }
+
               $positions = id(new PhabricatorProjectColumnPositionQuery())
                 ->setViewer($user)
                 ->withColumns(array($column))
@@ -397,7 +408,7 @@
               if ($order == PhabricatorProjectColumn::ORDER_NATURAL) {
                 // TODO: This is a little bit awkward, because PHP and JS use
                 // slightly different sort order parameters to achieve the same
-                // effect. It would be unify this a bit at some point.
+                // effect. It would be good to unify this a bit at some point.
                 $sort_map = array();
                 foreach ($positions as $position) {
                   $sort_map[$position->getObjectPHID()] = array(
@@ -414,6 +425,7 @@
 
               $data = array(
                 'sortMap' => $sort_map,
+                'removeFromBoard' => $remove_from_board,
               );
               break;
             case 'task':
diff --git a/webroot/rsrc/js/application/projects/behavior-project-boards.js b/webroot/rsrc/js/application/projects/behavior-project-boards.js
--- a/webroot/rsrc/js/application/projects/behavior-project-boards.js
+++ b/webroot/rsrc/js/application/projects/behavior-project-boards.js
@@ -204,6 +204,7 @@
     var new_data = JX.Stratcom.getData(new_card);
     var items = finditems(column);
     var edited = false;
+    var remove_index = null;
 
     for (var ii = 0; ii < items.length; ii++) {
       var item = items[ii];
@@ -212,6 +213,9 @@
       var phid = data.objectPHID;
 
       if (phid == new_data.objectPHID) {
+        if (r.data.removeFromBoard) {
+          remove_index = ii;
+        }
         items[ii] = new_card;
         data = new_data;
         edited = true;
@@ -226,6 +230,10 @@
       new_data.sort = r.data.sortMap[new_data.objectPHID] || new_data.sort;
     }
 
+    if (remove_index !== null) {
+      items.splice(remove_index, 1);
+    }
+
     items.sort(colsort);
 
     JX.DOM.setContent(column, items);