diff --git a/javascript/externs/web/webstorage.js b/javascript/externs/web/webstorage.js
index eee69d258145..7a41cccdd430 100644
--- a/javascript/externs/web/webstorage.js
+++ b/javascript/externs/web/webstorage.js
@@ -97,16 +97,40 @@ WindowLocalStorage.prototype.localStorage;
  */
 Window.prototype.localStorage;
 
+/**
+ * @record
+ * @extends {EventInit}
+ * @see https://html.spec.whatwg.org/multipage/webstorage.html#dictdef-storageeventinit
+ */
+function StorageEventInit() {}
+
+/** @type {(?string|undefined)} */
+StorageEventInit.prototype.key;
+
+/** @type {(?string|undefined)} */
+StorageEventInit.prototype.oldValue;
+
+/** @type {(?string|undefined)} */
+StorageEventInit.prototype.newValue;
+
+/** @type {(string|undefined)} */
+StorageEventInit.prototype.url;
+
+/** @type {(?Storage|undefined)} */
+StorageEventInit.prototype.storageArea;
+
 /**
  * This is the storage event interface.
- * @see http://www.w3.org/TR/2011/CR-webstorage-20111208/#the-storage-event
+ * @see https://html.spec.whatwg.org/multipage/webstorage.html#the-storageevent-interface
  * @extends {Event}
  * @constructor
+ * @param {string} type
+ * @param {StorageEventInit=} opt_eventInitDict
  */
-function StorageEvent() {}
+function StorageEvent(type, opt_eventInitDict) {}
 
 /**
- * @type {string}
+ * @type {?string}
  */
 StorageEvent.prototype.key;
 
@@ -132,17 +156,16 @@ StorageEvent.prototype.storageArea;
 
 /**
  * @param {string} typeArg
- * @param {boolean} canBubbleArg
- * @param {boolean} cancelableArg
- * @param {string} keyArg
- * @param {?string} oldValueArg
- * @param {?string} newValueArg
- * @param {string} urlArg
- * @param {?Storage} storageAreaArg
+ * @param {boolean=} canBubbleArg
+ * @param {boolean=} cancelableArg
+ * @param {?string=} keyArg
+ * @param {?string=} oldValueArg
+ * @param {?string=} newValueArg
+ * @param {string=} urlArg
+ * @param {?Storage=} storageAreaArg
  * @return {void}
  */
 StorageEvent.prototype.initStorageEvent = function(typeArg, canBubbleArg,
                                                    cancelableArg, keyArg,
                                                    oldValueArg, newValueArg,
                                                    urlArg, storageAreaArg) {};
-
diff --git a/javascript/ql/src/change-notes/2026-10-21-storageevent-constructor-arity.md b/javascript/ql/src/change-notes/2026-10-21-storageevent-constructor-arity.md
new file mode 100644
index 000000000000..4ebe50525e99
--- /dev/null
+++ b/javascript/ql/src/change-notes/2026-10-21-storageevent-constructor-arity.md
@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Valid arguments passed to the `StorageEvent` constructor no longer produce alerts from `js/superfluous-trailing-arguments`.
\ No newline at end of file
diff --git a/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/SpuriousArguments.expected b/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/SpuriousArguments.expected
index 40493b31b1ec..2ee2f0a55f4e 100644
--- a/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/SpuriousArguments.expected
+++ b/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/SpuriousArguments.expected
@@ -7,6 +7,7 @@
 | reflection.js:6:15:6:15 | 1 | Superfluous argument passed to $@. | reflection.js:1:1:1:23 | functio ... eturn;} | function f0 |
 | reflection.js:7:15:7:18 | 1 | Superfluous arguments passed to $@. | reflection.js:1:1:1:23 | functio ... eturn;} | function f0 |
 | reflection.js:12:18:12:18 | 2 | Superfluous argument passed to $@. | reflection.js:2:1:2:24 | functio ... eturn;} | function f1 |
+| storageEvent.js:14:33:14:39 | "extra" | Superfluous argument passed to $@. | externs.js:55:1:55:49 | functio ... ict) {} | function StorageEvent |
 | thisparameter.ts:4:11:4:12 | 45 | Superfluous argument passed to $@. | thisparameter.ts:1:1:1:45 | functio ... eturn;} | function foo |
 | transformstream.ts:15:33:15:34 | {} | Superfluous argument passed to $@. | externs.js:48:1:48:76 | functio ... egy) {} | function TransformStream |
 | tst.js:10:3:10:5 | g() | Superfluous argument passed to $@. | tst.js:1:1:4:1 | functio ... x+19;\\n} | function f |
diff --git a/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/externs.js b/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/externs.js
index cc3bf09cc149..f4a58aeb59bf 100644
--- a/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/externs.js
+++ b/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/externs.js
@@ -47,4 +47,11 @@ Number.parseFloat = function(num) {};
  */
 function TransformStream(transformer, writableStrategy, readableStrategy) {}
 
+/**
+ * @constructor
+ * @param {string} type
+ * @param {StorageEventInit=} opt_eventInitDict
+ */
+function StorageEvent(type, opt_eventInitDict) {}
+
 /** @externs */
diff --git a/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/storageEvent.js b/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/storageEvent.js
new file mode 100644
index 000000000000..43b709ca861a
--- /dev/null
+++ b/javascript/ql/test/query-tests/LanguageFeatures/SpuriousArguments/storageEvent.js
@@ -0,0 +1,14 @@
+new StorageEvent("storage");
+new StorageEvent("storage", {});
+new StorageEvent("storage", { key: "k", newValue: "v" });
+new StorageEvent("storage", {
+  key: null,
+  oldValue: null,
+  newValue: null,
+  url: "",
+  storageArea: null,
+  bubbles: false,
+  cancelable: false,
+  composed: false
+});
+new StorageEvent("storage", {}, "extra"); // $ Alert