The Stadion an der Alten Forsterei has been a fortress for Union ever since they were promoted to the Bundesliga in 2019, with Die Eisernen winning four of their six top-flight matches against Dortmund in front of their own supporters.
Nevertheless, Die Schwarzgelben started strongly here and moved in front within the opening 10 minutes.
Serhou Guirassy did well to bulldoze his way into the box and, although Frederik Ronnow got a slight touch to the ball as the Guinea striker poked the ball past him, it was not enough to avoid giving away a penalty. Emre Can made no mistake from 12 yards.
The remainder of the half was a hard-fought affair, with both sides relying on balls into the box to create opportunities. Fabio Silva went closest to scoring the game’s next goal, firing narrowly past the post after a series of Union blocks, while the home side’s best opening came when Diogo Leite headed over the crossbar.
After the interval, Union continued in their attempts to make it a physical affair, but BVB were up to the challenge.
Only a fantastic Ronnow stop low to his right denied Jobe Bellingham from the edge of the area, but he was beaten from the subsequent corner as Nico Schlotterbeck headed home from a tight angle - the Danish shot-stopper may feel he should have done better on that occasion, getting two strong hands to the attempt only to push it into the roof of the net.
This was not Dortmund’s most expansive performance, but it was perhaps one of their most professional as they dealt with everything Union had to throw at them. They even added extra gloss to the scoreline late on when Maximilian Beier hammered into the bottom corner from an angle.
After Bayern lost their first Bundesliga game of the campaign earlier on against Augsburg, Niko Kovac may once again believe they can win the title, even if they still have a lot of ground to make up.
For Union, this was their first defeat in six matches, but they will still end the weekend in the top half.
Flashscore Man of the Match: Nico Schlotterbeck (Borussia Dortmund)