The result saw fifth-placed Dortmund lose further ground in the hunt for a top-four finish and Champions League football next season. They have 43 points from 26 games, four less than Eintracht Frankfurt in fourth who celebrated a 5-2 home win over Union Berlin.
Haaland didn't look happy after the full time whistle 👀 pic.twitter.com/xNz2mVrGLi— ESPN FC (@ESPNFC) March 20, 2021
Haaland posted a message on Twitter an hour after the final whistle. He said: "Not a great result. We will use this as motivation to be back stronger! Thanks to all the @BVB fans for your continued support. We'll be back soon!"
Dortmund goalkeeper Marwin Hitz was disappointed with the outcome as the visitors allowed Cologne to turn the match on its head after Haaland struck a superb third-minute opener.
"We started really well and scored a nice first goal but then we disappeared," Hitz said.
"We sat back and lost possession too many times so it was definitely not a good afternoon for us. It's inexplicable that we made so many mistakes as we really needed to win this game."
Left-back Nico Shultz added: "We got too passive after taking the lead and we let Cologne back into the game. We needed to move the ball a lot better and we also weren't active enough defensively."
Haaland gave Dortmund a third-minute lead with a sublime finish as he took a long Emre Can ball in his stride and held off Jorge Mere's challenge before he steered a low shot through the legs of goalkeeper Timo Horn.
With Dortmund rattled, Ismail Jacobs turned the tide as he capped a fast break with an unstoppable shot from 15 metres in the 65th minute before Haaland hit the post at the other end.
Just when it seemed Cologne would complete the league double over Dortmund having beaten them 2-1 in the reverse fixture, Haaland popped up in front of goal to bundle in a 90th-minute assist by Ansgar Knauff.
Cologne stayed 14th on 23 points, two above the relegation spots.