Bring 1 inch of water to a boil in a medium saucepan. Add the broccoli to the pan. Cover the pan and reduce the heat to medium low. Cook until just tender, about 6 to 8 minutes. Drain and transfer the broccoli to a bowl.
Meanwhile, in a small saucepan, combine the sesame oil, vinegar, soy sauce, sugar, and sesame seeds; bring to a boil. Pour the sauce over the hot broccoli, tossing gently to coat thoroughly.