Rinse the Brussels sprouts under cold water. Trim the ends and remove any damaged outer leaves. Cut larger sprouts in half for more even cooking.
Bring the water to a boil and add the Brussels sprouts. Cover the pot and steam for about 5 minutes until sprouts are tender but still bright green.
Transfer the steamed sprouts to a bowl. Add butter, salt, and pepper, then gently toss to coat. Serve immediately.