St. Pauli’s hopes of improving on a 14th-place finish in 2024/25 were hit by the summer loss of Morgan Guilavogui and Elias Saad.
But after a positive start from St. Pauli, which saw Louis Oppie fire just wide of the target, Andreas Hountondji nearly filled the holes they left behind in style on 18 minutes, when he latched onto a defence-splitting pass and forced Gregor Kobel into saving at his right-hand post.
Dortmund took a while to get going, but they started becoming dominant after the midway point of the first half, with Pascal Gross being denied by Nikola Vasilj after latching onto the ball in the box.
Perhaps inevitably, it was Serhou Guirassy who struck first instead, when he brilliantly towered above the St. Pauli defence to power a header home from Marcel Sabitzer’s delivery into the box in the 34th minute.
The Guinea international also had an opportunity to net his second of the evening from the penalty spot just five minutes later, but Vasilj made a great save to keep St. Pauli in the game.
Almost poetically, St Pauli capitalised on that let-off after the restart and levelled after just five minutes. In similar circumstances to Dortmund’s opener, as Hountondji dwarfed the opposition defence to head home from Danel Sinani’s cross.
The momentum was now with the home side, and Mathias Pereira Lage came close to giving the hosts the lead, but his effort was comfortably saved by Kobel.
St. Pauli were punished for not taking the initiative when on top, as Dortmund made them pay following a slick team move which ended with Waldemar Anton sweeping the ball into the far corner.
The points were seemingly wrapped up minutes later with another sublime goal for the visitors. Gross clipped a ball over the top, and Julian Brandt controlled the ball before slotting into the far corner with a tidy finish.
But the home side were given a way back into the contest late on when Filippo Mane was sent off and gave a penalty away.
Sinani stepped up to cut the deficit to one goal with less than five minutes to go, and the turnaround was complete in the 89th minute, when Eric Smith drew the hosts level with a powerful effort into the bottom left corner.
Dortmund will have been left incensed after letting the two-goal lead slip, and an 11th consecutive opening day victory being spurned to the effect of giving Bayern Munich a head start in the title race.
Flashscore Man of the Match: Pascal Gross (Borussia Dortmund)