diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/DurationPrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/DurationPrototype.cpp
index 6f673b1b78..216240aad8 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/DurationPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/DurationPrototype.cpp
@@ -37,6 +37,9 @@ void DurationPrototype::initialize(GlobalObject& global_object)
     define_native_accessor(vm.names.nanoseconds, nanoseconds_getter, {}, Attribute::Configurable);
     define_native_accessor(vm.names.sign, sign_getter, {}, Attribute::Configurable);
     define_native_accessor(vm.names.blank, blank_getter, {}, Attribute::Configurable);
+
+    u8 attr = Attribute::Writable | Attribute::Configurable;
+    define_native_function(vm.names.valueOf, value_of, 0, attr);
 }
 
 static Duration* typed_this(GlobalObject& global_object)
@@ -215,4 +218,12 @@ JS_DEFINE_NATIVE_FUNCTION(DurationPrototype::blank_getter)
     return Value(false);
 }
 
+// 7.3.25 Temporal.Duration.prototype.valueOf ( ), https://tc39.es/proposal-temporal/#sec-temporal.duration.prototype.valueof
+JS_DEFINE_NATIVE_FUNCTION(DurationPrototype::value_of)
+{
+    // 1. Throw a TypeError exception.
+    vm.throw_exception<TypeError>(global_object, ErrorType::Convert, "Temporal.Duration", "a primitive value");
+    return {};
+}
+
 }
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/DurationPrototype.h b/Userland/Libraries/LibJS/Runtime/Temporal/DurationPrototype.h
index e5d531f3f0..85b02404cc 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/DurationPrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/DurationPrototype.h
@@ -31,6 +31,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(nanoseconds_getter);
     JS_DECLARE_NATIVE_FUNCTION(sign_getter);
     JS_DECLARE_NATIVE_FUNCTION(blank_getter);
+    JS_DECLARE_NATIVE_FUNCTION(value_of);
 };
 
 }
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/Duration/Duration.prototype.valueOf.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/Duration/Duration.prototype.valueOf.js
new file mode 100644
index 0000000000..ab779bfbb0
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/Duration/Duration.prototype.valueOf.js
@@ -0,0 +1,7 @@
+test("errors", () => {
+    test("throws TypeError", () => {
+        expect(() => {
+            new Temporal.Duration().valueOf();
+        }).toThrowWithMessage(TypeError, "Cannot convert Temporal.Duration to a primitive value");
+    });
+});