Michy Batshuayi scored his third goal in his second game for Borussia Dortmund, as Marco Reus returned from an eight-month injury lay-off.
Chelsea loanee Batshuayi converted Christian Pulisic's cross from close range as Dortmund beat Hamburg to remain third.
Reus, who last played when he ruptured his ligaments in May's German Cup final win over Eintracht Frankfurt, captained the side.
Mario Gotze chipped in a late second.
Elsewhere, Eintracht Frankfurt remain in the Champions League places after beating bottom club Cologne 4-2.
Fifth-placed Bayer Leverkusen lost 2-0 at home to Hertha Berlin. Hoffenheim beat Mainz 4-2, and Hannover beat Freiburg 2-1.