Raul Bobadilla scored the only goal in a 1-0 victory for Augsburg as Borussia Dortmund slipped to their 11th loss of the Bundesliga season.
It was a bright start from Jurgen Klopp's side, who were aiming to climb off the bottom of the table, as the lively Marco Reus tested the Augsburg defence with a clever run before firing an effort just past the post.
However, Augsburg refused to be dominated by the hosts, and possession was shared equally for long spells of the match as Dortmund continued to look short of their best.
Pierre-Emerick Aubameyang thought he had broken the deadlock when he got a vital touch on a powerful effort from Reus, but an offside flag cut short the forward's celebrations.
Augsburg were inches away from taking the lead before the break when Paul Verhaegh ventured forward unchallenged before hitting a low shot a few inches wide.
Verhaegh's close call was a sign of things to come, as the Dortmund supporters were left frustrated once again early in the second half when Halil Altintop's persistence on the edge of the box saw the ball break to Bobadilla, who drilled his strike past a helpless Roman Weidenfeller.
It could have been 2-0 just a few moments later, but Kevin Grosskreutz made a crucial block to keep out Tobias Werner's effort after the midfielder had evaded a couple of challenges in the box.
However, Dortmund were gifted a way back into the match when Christoph Janker was shown a straight red card for bringing down Aubameyang as the Gabon international sprinted clear of the Augsburg defence.
Augsburg defended stubbornly after the numerical advantage was handed to the home side, and Dortmund were unable to breach the visiting defence as Henrikh Mkhitaryan fired the best chance straight at Alex Manninger.