Jadon Sancho and Erling Haaland scored two goals apiece to crush RB Leipzig 4-1.
Sancho curled a superb shot into the top corner in the fifth minute.
He added another with a quick break on the stroke of halftime after Haaland, powered into the box and flicked the ball past keeper Peter Gulacsi.
Borussia Dortmund were brutally efficient in the first half, scoring with each of their three shots on target.
Leipzig launched a late attempt at a comeback, pulling a goal back with a thundering drive from Dani Olmo in the 71st minute.
Sancho wasted a golden chance to complete his hat-trick before Haaland rifled in his second goal.
It was Dortmund’s fifth German Cup triumph and their first since 2017.
Meanwhile Leipzig missed out again on winning their first silverware.
Dortmund’s attention can now turn towards ensuring Champions League qualification.
They sit fourth in the Bundesliga table, one point above fifth-place Eintracht Frankfurt, with two games of the season left to go.