Cologne were trailing 2-1 after Hoffenheim's Adam Daghim and Ozan Kabak had struck either side of an excellent El Mala equaliser. Dallinga came off the bench in the 65th minute to replace Ragnar Ache. He made a significant impact, scoring two goals in quick succession to hand his new side a 3-2 lead with eight minutes to go.
The 20-year-old striker, who joined Cologne on loan from Serie A side Bologna just under two weeks ago, showed great alertness to pounce on a loose ball in the area and steer it home with conviction. Dallinga's impressive debut was praised by head coach René Wagner, who said: "If you look at the scores, the Bundesliga always has a lot of goals, and that was the case again today. That was what attracted me about coming here and today I showed why I came."
Cologne's next challenge is a trip to take on VfB Stuttgart on Friday.