diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index 3cbe8024b9e..0f2209c00ea 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -2230,6 +2230,14 @@ impl NodeMethods for Node {
         }
     }
 
+    // https://dom.spec.whatwg.org/#dom-node-issamenode
+    fn IsSameNode(&self, otherNode: Option<&Node>) -> bool {
+        match otherNode {
+            Some(node) => self == node,
+            None => false,
+        }
+    }
+
     // https://dom.spec.whatwg.org/#dom-node-comparedocumentposition
     fn CompareDocumentPosition(&self, other: &Node) -> u16 {
         if self == other {
diff --git a/components/script/dom/webidls/Node.webidl b/components/script/dom/webidls/Node.webidl
index 0c3311cb647..f727fa98660 100644
--- a/components/script/dom/webidls/Node.webidl
+++ b/components/script/dom/webidls/Node.webidl
@@ -58,6 +58,8 @@ interface Node : EventTarget {
   Node cloneNode(optional boolean deep = false);
   [Pure]
   boolean isEqualNode(Node? node);
+  [Pure]
+  boolean isSameNode(Node? otherNode); // historical alias of ===
 
   const unsigned short DOCUMENT_POSITION_DISCONNECTED = 0x01;
   const unsigned short DOCUMENT_POSITION_PRECEDING = 0x02;
diff --git a/tests/wpt/metadata/MANIFEST.json b/tests/wpt/metadata/MANIFEST.json
index bfb83729c78..533d663e71a 100644
--- a/tests/wpt/metadata/MANIFEST.json
+++ b/tests/wpt/metadata/MANIFEST.json
@@ -35235,6 +35235,12 @@
             "path": "dom/nodes/Element-hasAttributes.html",
             "url": "/dom/nodes/Element-hasAttributes.html"
           }
+        ],
+        "dom/nodes/Node-isSameNode.html": [
+          {
+            "path": "dom/nodes/Node-isSameNode.html",
+            "url": "/dom/nodes/Node-isSameNode.html"
+          }
         ]
       }
     },
diff --git a/tests/wpt/metadata/dom/interfaces.html.ini b/tests/wpt/metadata/dom/interfaces.html.ini
index 68196d519d3..2569ebac143 100644
--- a/tests/wpt/metadata/dom/interfaces.html.ini
+++ b/tests/wpt/metadata/dom/interfaces.html.ini
@@ -186,45 +186,18 @@
   [Node interface: attribute isConnected]
     expected: FAIL
 
-  [Node interface: operation isSameNode(Node)]
-    expected: FAIL
-
   [Node interface: new Document() must inherit property "isConnected" with the proper type (15)]
     expected: FAIL
 
-  [Node interface: new Document() must inherit property "isSameNode" with the proper type (31)]
-    expected: FAIL
-
-  [Node interface: calling isSameNode(Node) on new Document() with too few arguments must throw TypeError]
-    expected: FAIL
-
   [Node interface: xmlDoc must inherit property "isConnected" with the proper type (15)]
     expected: FAIL
 
-  [Node interface: xmlDoc must inherit property "isSameNode" with the proper type (31)]
-    expected: FAIL
-
-  [Node interface: calling isSameNode(Node) on xmlDoc with too few arguments must throw TypeError]
-    expected: FAIL
-
   [Node interface: document.doctype must inherit property "isConnected" with the proper type (15)]
     expected: FAIL
 
-  [Node interface: document.doctype must inherit property "isSameNode" with the proper type (31)]
-    expected: FAIL
-
-  [Node interface: calling isSameNode(Node) on document.doctype with too few arguments must throw TypeError]
-    expected: FAIL
-
   [Node interface: document.createDocumentFragment() must inherit property "isConnected" with the proper type (15)]
     expected: FAIL
 
-  [Node interface: document.createDocumentFragment() must inherit property "isSameNode" with the proper type (31)]
-    expected: FAIL
-
-  [Node interface: calling isSameNode(Node) on document.createDocumentFragment() with too few arguments must throw TypeError]
-    expected: FAIL
-
   [ShadowRoot interface: existence and properties of interface object]
     expected: FAIL
 
@@ -276,12 +249,6 @@
   [Node interface: element must inherit property "isConnected" with the proper type (15)]
     expected: FAIL
 
-  [Node interface: element must inherit property "isSameNode" with the proper type (31)]
-    expected: FAIL
-
-  [Node interface: calling isSameNode(Node) on element with too few arguments must throw TypeError]
-    expected: FAIL
-
   [Text interface: attribute assignedSlot]
     expected: FAIL
 
@@ -291,27 +258,8 @@
   [Node interface: document.createTextNode("abc") must inherit property "isConnected" with the proper type (15)]
     expected: FAIL
 
-  [Node interface: document.createTextNode("abc") must inherit property "isSameNode" with the proper type (31)]
-    expected: FAIL
-
-  [Node interface: calling isSameNode(Node) on document.createTextNode("abc") with too few arguments must throw TypeError]
-    expected: FAIL
-
   [Node interface: xmlDoc.createProcessingInstruction("abc", "def") must inherit property "isConnected" with the proper type (15)]
     expected: FAIL
 
-  [Node interface: xmlDoc.createProcessingInstruction("abc", "def") must inherit property "isSameNode" with the proper type (31)]
-    expected: FAIL
-
-  [Node interface: calling isSameNode(Node) on xmlDoc.createProcessingInstruction("abc", "def") with too few arguments must throw TypeError]
-    expected: FAIL
-
   [Node interface: document.createComment("abc") must inherit property "isConnected" with the proper type (15)]
     expected: FAIL
-
-  [Node interface: document.createComment("abc") must inherit property "isSameNode" with the proper type (31)]
-    expected: FAIL
-
-  [Node interface: calling isSameNode(Node) on document.createComment("abc") with too few arguments must throw TypeError]
-    expected: FAIL
-
diff --git a/tests/wpt/web-platform-tests/dom/nodes/Node-isSameNode.html b/tests/wpt/web-platform-tests/dom/nodes/Node-isSameNode.html
new file mode 100644
index 00000000000..884fdd50490
--- /dev/null
+++ b/tests/wpt/web-platform-tests/dom/nodes/Node-isSameNode.html
@@ -0,0 +1,100 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>Node.prototype.isSameNode</title>
+<link rel=help href="https://dom.spec.whatwg.org/#dom-node-issamenode">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+"use strict";
+
+test(function() {
+
+  var doctype1 = document.implementation.createDocumentType("qualifiedName", "publicId", "systemId");
+  var doctype2 = document.implementation.createDocumentType("qualifiedName", "publicId", "systemId");
+
+  assert_true(doctype1.isSameNode(doctype1), "self-comparison");
+  assert_false(doctype1.isSameNode(doctype2), "same properties");
+  assert_false(doctype1.isSameNode(null), "with null other node");
+}, "doctypes should be comapred on reference");
+
+test(function() {
+
+  var element1 = document.createElementNS("namespace", "prefix:localName");
+  var element2 = document.createElementNS("namespace", "prefix:localName");
+
+  assert_true(element1.isSameNode(element1), "self-comparison");
+  assert_false(element1.isSameNode(element2), "same properties");
+  assert_false(element1.isSameNode(null), "with null other node");
+
+}, "elements should be compared on reference");
+
+test(function() {
+
+  var element1 = document.createElement("element");
+  element1.setAttributeNS("namespace", "prefix:localName", "value");
+
+  var element2 = document.createElement("element");
+  element2.setAttributeNS("namespace", "prefix:localName", "value");
+
+  assert_true(element1.isSameNode(element1), "self-comparison");
+  assert_false(element1.isSameNode(element2), "same properties");
+  assert_false(element1.isSameNode(null), "with null other node");
+
+}, "elements should be compared on reference");
+
+test(function() {
+
+  var pi1 = document.createProcessingInstruction("target", "data");
+  var pi2 = document.createProcessingInstruction("target", "data");
+
+  assert_true(pi1.isSameNode(pi1), "self-comparison");
+  assert_false(pi1.isSameNode(pi2), "different target");
+  assert_false(pi1.isSameNode(null), "with null other node");
+
+}, "processing instructions should be compared on reference");
+
+test(function() {
+
+  var text1 = document.createTextNode("data");
+  var text2 = document.createTextNode("data");
+
+  assert_true(text1.isSameNode(text1), "self-comparison");
+  assert_false(text1.isSameNode(text2), "same properties");
+  assert_false(text1.isSameNode(null), "with null other node");
+
+}, "text nodes should be compared on reference");
+
+test(function() {
+
+  var comment1 = document.createComment("data");
+  var comment2 = document.createComment("data");
+
+  assert_true(comment1.isSameNode(comment1), "self-comparison");
+  assert_false(comment1.isSameNode(comment2), "same properties");
+  assert_false(comment1.isSameNode(null), "with null other node");
+
+}, "comments should be compared on reference");
+
+test(function() {
+
+  var documentFragment1 = document.createDocumentFragment();
+  var documentFragment2 = document.createDocumentFragment();
+
+  assert_true(documentFragment1.isSameNode(documentFragment1), "self-comparison");
+  assert_false(documentFragment1.isSameNode(documentFragment2), "same properties");
+  assert_false(documentFragment1.isSameNode(null), "with null other node");
+
+}, "document fragments should be compared on reference");
+
+test(function() {
+
+  var document1 = document.implementation.createDocument("", "");
+  var document2 = document.implementation.createDocument("", "");
+
+  assert_true(document1.isSameNode(document1), "self-comparison");
+  assert_false(document1.isSameNode(document2), "another empty XML document");
+  assert_false(document1.isSameNode(null), "with null other node");
+
+}, "documents should not be compared on reference");
+
+</script>