diff --git a/CHANGELOG.md b/CHANGELOG.md
index 99f4308f9a0a..68f5c1dca6ec 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -27,6 +27,7 @@
 - Added `value` argument of `URLSearchParams.prototype.{ has, delete }`, [url/735](https://github.com/whatwg/url/pull/735)
 - Fixed some cases of increasing buffer size in `ArrayBuffer.prototype.{ transfer, transferToFixedLength }` polyfills
 - Fixed awaiting async `AsyncDisposableStack.prototype.adopt` callback, [#1258](https://github.com/zloirock/core-js/issues/1258)
+- Fixed `URLSearchParams#size` in ES3 engines (IE8-)
 - Added TypeScript definitions to `core-js-compat`, [#1235](https://github.com/zloirock/core-js/issues/1235), thanks [@susnux](https://github.com/susnux)
 - Compat data improvements:
   - [`Set.prototype.difference`](https://github.com/tc39/proposal-set-methods) that was missed in Bun because of [a bug](https://github.com/oven-sh/bun/issues/2309) added in 0.6.0
diff --git a/packages/core-js/modules/web.url-search-params.constructor.js b/packages/core-js/modules/web.url-search-params.constructor.js
index 9f96717a68a4..af7bdf590ec7 100644
--- a/packages/core-js/modules/web.url-search-params.constructor.js
+++ b/packages/core-js/modules/web.url-search-params.constructor.js
@@ -205,7 +205,7 @@ var URLSearchParamsConstructor = function URLSearchParams(/* init */) {
   anInstance(this, URLSearchParamsPrototype);
   var init = arguments.length > 0 ? arguments[0] : undefined;
   var state = setInternalState(this, new URLSearchParamsState(init));
-  if (!DESCRIPTORS) this.length = state.entries.length;
+  if (!DESCRIPTORS) this.size = state.entries.length;
 };
 
 var URLSearchParamsPrototype = URLSearchParamsConstructor.prototype;
@@ -237,7 +237,7 @@ defineBuiltIns(URLSearchParamsPrototype, {
         if (value !== undefined) break;
       } else index++;
     }
-    if (!DESCRIPTORS) this.length = entries.length;
+    if (!DESCRIPTORS) this.size = entries.length;
     state.updateURL();
   },
   // `URLSearchParams.prototype.get` method
@@ -302,7 +302,7 @@ defineBuiltIns(URLSearchParamsPrototype, {
       }
     }
     if (!found) push(entries, { key: key, value: val });
-    if (!DESCRIPTORS) this.length = entries.length;
+    if (!DESCRIPTORS) this.size = entries.length;
     state.updateURL();
   },
   // `URLSearchParams.prototype.sort` method