Both sides named strong teams for the match as Thomas Tuchel chases his first major piece of silverware with Dortmund and Carlo Ancelotti pursed a domestic double in his first season in Germany.
It was Dortmund who took the lead as some slack defending from Javi Martinez presented Marco Reus with a tap-in that he duly took.
However Bayern responded really well with first Martinez equalising with a powerful header, and then his defensive partner Mats Hummels finishing well to complete the turnaround.
In the second-half Dortmund came out pressing as they desperately looked for the equaliser.
They put Bayern under intense pressure and eventually their patience was rewarded when a deep cross from Dembele found its way to Pierre-Emerick Aubameyang who headed into the empty net.
Minutes later they had taken the lead when Reus slipped the ball out to Dembele and he cut back onto his left before curling a shot into the top corner off the bar.
Read the full article on eurosport.co.uk: Dembele sinks Bayern as Dortmund seal dramatic cup win