كتب : Sherif Tarek
The Visitors took the lead on 16 minutes when Jan Schlaudraff opened the scoring.
Pedro Geromel netted the equalizer three minutes before the interval, and Wilfried Sanou scored the winner for Cologne on 71 minutes.
Six-placed Cologne now have 19 points, while Hannover have 12 points, just four above the relegation zone.