diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp
index 50c83ed960..f869437707 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.cpp
@@ -69,6 +69,7 @@ void ZonedDateTimePrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.withPlainDate, with_plain_date, 1, attr);
     define_native_function(vm.names.withTimeZone, with_time_zone, 1, attr);
     define_native_function(vm.names.withCalendar, with_calendar, 1, attr);
+    define_native_function(vm.names.add, add, 1, attr);
     define_native_function(vm.names.equals, equals, 1, attr);
     define_native_function(vm.names.toString, to_string, 0, attr);
     define_native_function(vm.names.toLocaleString, to_locale_string, 0, attr);
@@ -813,6 +814,32 @@ JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::with_calendar)
     return MUST(create_temporal_zoned_date_time(global_object, zoned_date_time->nanoseconds(), zoned_date_time->time_zone(), *calendar));
 }
 
+// 6.3.35 Temporal.ZonedDateTime.prototype.add ( temporalDurationLike [ , options ] ), https://tc39.es/proposal-temporal/#sec-temporal.zoneddatetime.prototype.add
+JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::add)
+{
+    // 1. Let zonedDateTime be the this value.
+    // 2. Perform ? RequireInternalSlot(zonedDateTime, [[InitializedTemporalZonedDateTime]]).
+    auto* zoned_date_time = TRY(typed_this_object(global_object));
+
+    // 3. Let duration be ? ToLimitedTemporalDuration(temporalDurationLike, « »).
+    auto duration = TRY(to_limited_temporal_duration(global_object, vm.argument(0), {}));
+
+    // 4. Set options to ? GetOptionsObject(options).
+    auto* options = TRY(get_options_object(global_object, vm.argument(1)));
+
+    // 5. Let timeZone be zonedDateTime.[[TimeZone]].
+    auto& time_zone = zoned_date_time->time_zone();
+
+    // 6. Let calendar be zonedDateTime.[[Calendar]].
+    auto& calendar = zoned_date_time->calendar();
+
+    // 7. Let epochNanoseconds be ? AddZonedDateTime(zonedDateTime.[[Nanoseconds]], timeZone, calendar, duration.[[Years]], duration.[[Months]], duration.[[Weeks]], duration.[[Days]], duration.[[Hours]], duration.[[Minutes]], duration.[[Seconds]], duration.[[Milliseconds]], duration.[[Microseconds]], duration.[[Nanoseconds]], options).
+    auto* epoch_nanoseconds = TRY(add_zoned_date_time(global_object, zoned_date_time->nanoseconds(), &time_zone, calendar, duration.years, duration.months, duration.weeks, duration.days, duration.hours, duration.minutes, duration.seconds, duration.milliseconds, duration.microseconds, duration.nanoseconds, options));
+
+    // 8. Return ! CreateTemporalZonedDateTime(epochNanoseconds, timeZone, calendar).
+    return MUST(create_temporal_zoned_date_time(global_object, *epoch_nanoseconds, time_zone, calendar));
+}
+
 // 6.3.40 Temporal.ZonedDateTime.prototype.equals ( other ), https://tc39.es/proposal-temporal/#sec-temporal.zoneddatetime.prototype.equals
 JS_DEFINE_NATIVE_FUNCTION(ZonedDateTimePrototype::equals)
 {
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h b/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h
index c184db2213..73f1b2e854 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/ZonedDateTimePrototype.h
@@ -53,6 +53,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(with_plain_date);
     JS_DECLARE_NATIVE_FUNCTION(with_time_zone);
     JS_DECLARE_NATIVE_FUNCTION(with_calendar);
+    JS_DECLARE_NATIVE_FUNCTION(add);
     JS_DECLARE_NATIVE_FUNCTION(equals);
     JS_DECLARE_NATIVE_FUNCTION(to_string);
     JS_DECLARE_NATIVE_FUNCTION(to_locale_string);
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.prototype.add.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.prototype.add.js
new file mode 100644
index 0000000000..9798e36433
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/ZonedDateTime/ZonedDateTime.prototype.add.js
@@ -0,0 +1,62 @@
+describe("correct behavior", () => {
+    test("length is 1", () => {
+        expect(Temporal.ZonedDateTime.prototype.add).toHaveLength(1);
+    });
+
+    test("basic functionality", () => {
+        const plainDateTime = new Temporal.PlainDateTime(2021, 11, 12, 0, 22, 30, 100, 200, 300);
+        const timeZone = new Temporal.TimeZone("UTC");
+        const zonedDateTime = plainDateTime.toZonedDateTime(timeZone);
+        const dayDuration = new Temporal.Duration(0, 0, 0, 1);
+        const result = zonedDateTime.add(dayDuration);
+
+        expect(zonedDateTime.day).toBe(12);
+        expect(zonedDateTime.epochNanoseconds).toBe(1636676550100200300n);
+
+        expect(result.day).toBe(13);
+        expect(result.epochNanoseconds).toBe(1636762950100200300n);
+    });
+
+    test("duration-like object", () => {
+        const plainDateTime = new Temporal.PlainDateTime(2021, 11, 12, 0, 22, 30, 100, 200, 300);
+        const timeZone = new Temporal.TimeZone("UTC");
+        const zonedDateTime = plainDateTime.toZonedDateTime(timeZone);
+        const dayDuration = { days: 1 };
+        const result = zonedDateTime.add(dayDuration);
+
+        expect(zonedDateTime.day).toBe(12);
+        expect(zonedDateTime.epochNanoseconds).toBe(1636676550100200300n);
+
+        expect(result.day).toBe(13);
+        expect(result.epochNanoseconds).toBe(1636762950100200300n);
+    });
+
+    // FIXME: Unskip when ParseTemporalDurationString is implemented.
+    test.skip("duration string", () => {
+        const plainDateTime = new Temporal.PlainDateTime(2021, 11, 12, 0, 22, 30, 100, 200, 300);
+        const timeZone = new Temporal.TimeZone("UTC");
+        const zonedDateTime = plainDateTime.toZonedDateTime(timeZone);
+        const dayDuration = "P1D";
+        const result = zonedDateTime.add(dayDuration);
+
+        expect(zonedDateTime.day).toBe(12);
+        expect(zonedDateTime.epochNanoseconds).toBe(1636676550100200300n);
+
+        expect(result.day).toBe(13);
+        expect(result.epochNanoseconds).toBe(1636762950100200300n);
+    });
+});
+
+describe("errors", () => {
+    test("this value must be a Temporal.ZonedDateTime object", () => {
+        expect(() => {
+            Temporal.ZonedDateTime.prototype.add.call("foo");
+        }).toThrowWithMessage(TypeError, "Not an object of type Temporal.ZonedDateTime");
+    });
+
+    test("invalid duration-like object", () => {
+        expect(() => {
+            new Temporal.ZonedDateTime(1n, {}).add({});
+        }).toThrowWithMessage(TypeError, "Invalid duration-like object");
+    });
+});