diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
index 4b2795d5dc..3ce7d3785d 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
@@ -23,6 +23,17 @@ void PlainDateTimePrototype::initialize(GlobalObject& global_object)
 
     // 5.3.2 Temporal.PlainDateTime.prototype[ @@toStringTag ], https://tc39.es/proposal-temporal/#sec-temporal.plaindatetime.prototype-@@tostringtag
     define_direct_property(*vm.well_known_symbol_to_string_tag(), js_string(vm.heap(), "Temporal.PlainDateTime"), Attribute::Configurable);
+
+    u8 attr = Attribute::Writable | Attribute::Configurable;
+    define_native_function(vm.names.valueOf, value_of, 0, attr);
+}
+
+// 5.3.35 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.
+    vm.throw_exception<TypeError>(global_object, ErrorType::Convert, "Temporal.PlainDateTime", "a primitive value");
+    return {};
 }
 
 }
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
index 434d542324..0b9ba502e3 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
@@ -17,6 +17,9 @@ public:
     explicit PlainDateTimePrototype(GlobalObject&);
     virtual void initialize(GlobalObject&) override;
     virtual ~PlainDateTimePrototype() override = default;
+
+private:
+    JS_DECLARE_NATIVE_FUNCTION(value_of);
 };
 
 }
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.valueOf.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.valueOf.js
new file mode 100644
index 0000000000..48a3812334
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.valueOf.js
@@ -0,0 +1,10 @@
+test("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"
+        );
+    });
+});