diff --git a/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp b/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
index 0814ca7d31b..548824e9c44 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
+++ b/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
@@ -68,6 +68,7 @@ void PlainDateTimePrototype::initialize(Realm& realm)
     define_native_function(realm, vm.names.toString, to_string, 0, attr);
     define_native_function(realm, vm.names.toLocaleString, to_locale_string, 0, attr);
     define_native_function(realm, vm.names.toJSON, to_json, 0, attr);
+    define_native_function(realm, vm.names.valueOf, value_of, 0, attr);
     define_native_function(realm, vm.names.toPlainDate, to_plain_date, 0, attr);
     define_native_function(realm, vm.names.toPlainTime, to_plain_time, 0, attr);
 }
@@ -550,6 +551,13 @@ JS_DEFINE_NATIVE_FUNCTION(PlainDateTimePrototype::to_json)
     return PrimitiveString::create(vm, iso_date_time_to_string(date_time->iso_date_time(), date_time->calendar(), Auto {}, ShowCalendar::Auto));
 }
 
+// 5.3.37 Temporal.PlainDateTime.prototype.valueOf ( ), https://tc39.es/proposal-temporal/#sec-temporal.plaindatetime.prototype.valueof
+JS_DEFINE_NATIVE_FUNCTION(PlainDateTimePrototype::value_of)
+{
+    // 1. Throw a TypeError exception.
+    return vm.throw_completion<TypeError>(ErrorType::Convert, "Temporal.PlainDateTime", "a primitive value");
+}
+
 // 5.3.39 Temporal.PlainDateTime.prototype.toPlainDate ( ), https://tc39.es/proposal-temporal/#sec-temporal.plaindatetime.prototype.toplaindate
 JS_DEFINE_NATIVE_FUNCTION(PlainDateTimePrototype::to_plain_date)
 {
diff --git a/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h b/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
index 0091eeb3d29..7913a1ea1f8 100644
--- a/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
+++ b/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
@@ -57,6 +57,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(to_string);
     JS_DECLARE_NATIVE_FUNCTION(to_locale_string);
     JS_DECLARE_NATIVE_FUNCTION(to_json);
+    JS_DECLARE_NATIVE_FUNCTION(value_of);
     JS_DECLARE_NATIVE_FUNCTION(to_plain_date);
     JS_DECLARE_NATIVE_FUNCTION(to_plain_time);
 };
diff --git a/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.valueOf.js b/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.valueOf.js
new file mode 100644
index 00000000000..ec9daaee505
--- /dev/null
+++ b/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.valueOf.js
@@ -0,0 +1,10 @@
+describe("errors", () => {
+    test("throws TypeError", () => {
+        expect(() => {
+            new Temporal.PlainDateTime(2021, 7, 22, 19, 54, 38).valueOf();
+        }).toThrowWithMessage(
+            TypeError,
+            "Cannot convert Temporal.PlainDateTime to a primitive value"
+        );
+    });
+});