Late Hannover double stuns Dortmund
Beaten 2-1 at home by Hertha Berlin a week ago, Dortmund went ahead when Japanese midfielder Shinji Kagawa beat two defenders to score from 12 metres just after the hour.
However, they fell apart when Tunisian defender Karim Haggui headed the equaliser from a corner for Hanover in the 86th minute and Ivorian forward Didier Ya Konan fired the winner from the edge of the penalty area two minutes later.
Hanover substitute Artur Sobiech was sent off in stoppage-time for an ugly tackle from behind after seven minutes on the field.
Dortmund are a modest 11th with seven points from six games while Hannover have 11.