Elsewhere, Hoffenheim cruised to a 2-0 triumph over Augsburg owing to first-half goals from Adam Szalai and Tarik Elyounoussi."
Berlin, Aug 24 - Bayer Leverkusen upset Borussia Dortmund 2-0 while Hannover came from behind to stun Schalke 2-1 in the first round of the German Bundesliga.
Last year's runner-up Dortmund suffered a setback in their first match as Leverkusen reaped a 2-0 away win, owing to goals from Karim Bellarabi and Stefan Kiessling Saturday, reports Xinhua.
The Werkself got off to a bright start as Bellarabi surprised Dortmund with the earliest goal in the Bundesliga history.
After the kickoff, Leverkusen immediately attacked to see Bellarabi tapping home from inside the box just nine seconds into the encounter.
Dortmund seemed stunned and failed to find a response to Leverkusen's early opener. The BVB pressed in the second half but lacked the cutting edge.
In the closing period, Dortmund piled on the pressure as Matthias Ginter and Pierre Emerick Aubameyang nearly equalised.
However, it was Leverkusen that killed the game off against the run of play in the dying minutes, when Stefan Kiessling utilised a square pass by Bellarabi to seal the deal.
Meanwhile, Hannover shocked Schalke with a 2-1-comeback win thanks to the goals from Edgar Prib and Joselu.
Schalke had to make amendments following their painful first round exit at the German Cup against third division side Dresden.
However, the Royal Blues suffered their second setback as they wasted a 1-0 lead to lose 1-2 to clinical Hannover.
Berlin squandered a two-goal lead to share the spoils with Bremen following a 2-2 draw.
Elsewhere, Hoffenheim cruised to a 2-0 triumph over Augsburg owing to first-half goals from Adam Szalai and Tarik Elyounoussi.
Frankfurt's Haris Seferovic winner secured the Eagles a 1-0 victory over Freiburg while newly promoted Cologne shared the points with Hamburg following a goalless draw.