--- a/browser/components/extensions/parent/ext-tabs.js
+++ b/browser/components/extensions/parent/ext-tabs.js
@@ -1091,30 +1091,20 @@ this.tabs = class extends ExtensionAPI {
 
           let gBrowser = nativeTab.ownerGlobal.gBrowser;
           let newTab = gBrowser.duplicateTab(nativeTab);
 
           tabListener.blockTabUntilRestored(newTab);
 
           return new Promise(resolve => {
             // We need to use SSTabRestoring because any attributes set before
-            // are ignored. SSTabRestored is too late and results in a jump in
-            // the UI. See http://bit.ly/session-store-api for more information.
+            // are ignored.
             newTab.addEventListener(
               "SSTabRestoring",
               function() {
-                // As the tab is restoring, move it to the correct position.
-
-                // Pinned tabs that are duplicated are inserted
-                // after the existing pinned tab and pinned.
-                if (nativeTab.pinned) {
-                  gBrowser.pinTab(newTab);
-                }
-                gBrowser.moveTabTo(newTab, nativeTab._tPos + 1);
-
                 gBrowser.selectedTab = newTab;
                 resolve(tabManager.convert(newTab));
               },
               { once: true }
             );
           });
         },
 

--- a/browser/components/extensions/test/browser/browser_ext_tabs_duplicate.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_duplicate.js
@@ -150,20 +150,20 @@ add_task(async function testDuplicatePin
       browser.tabs.query(
         {
           lastFocusedWindow: true,
         },
         function(tabs) {
           // Duplicate the pinned tab, example.net.
           browser.tabs.duplicate(tabs[0].id, tab => {
             browser.test.assertEq("http://example.net/", tab.url);
-            // Should be the second tab, next to the one duplicated.
+            // Should be the second tab, next to the original.
             browser.test.assertEq(1, tab.index);
-            // Should be pinned.
-            browser.test.assertTrue(tab.pinned);
+            // Duplicated tab is not pinned, even if the original tab is.
+            browser.test.assertFalse(tab.pinned);
 
             browser.tabs.remove([tabs[0].id, tab.id]);
             browser.test.notifyPass("tabs.duplicate.pinned");
           });
         }
       );
     },
   });