--- a/browser/base/content/tabview/items.js
+++ b/browser/base/content/tabview/items.js
@@ -963,35 +963,40 @@ let Items = {
     if (rows == 1) {
       tabWidth = Math.min(tabWidth, (bounds.height - 2 * itemMargin) / tabAspect);
       tabHeight = tabWidth * tabAspect;
     }
     
     if (options.return == 'widthAndColumns')
       return {childWidth: tabWidth, columns: columns};
 
-    var box = new Rect(bounds.left, bounds.top, tabWidth, tabHeight);
+    let initialOffset = 0;
+    if (UI.rtl) {
+      initialOffset = bounds.width - tabWidth;
+    }
+    var box = new Rect(bounds.left + initialOffset, bounds.top, tabWidth, tabHeight);
+
     var column = 0;
 
     for (let a = 0; a < count; a++) {
       rects.push(new Rect(box));
       if (items && a < items.length) {
         let item = items[a];
         if (!item.locked.bounds) {
           item.setBounds(box, immediately);
           item.setRotation(0);
           if (options.z)
             item.setZ(options.z);
         }
       }
 
-      box.left += box.width + padding;
+      box.left += (UI.rtl ? -1 : 1) * (box.width + padding);
       column++;
       if (column == columns) {
-        box.left = bounds.left;
+        box.left = bounds.left + initialOffset;
         box.top += (box.height * yScale) + padding;
         column = 0;
       }
     }
 
     return rects;
   },