Bellingham had put Dortmund on course for an unexpected victory in the Champions League with a header early in the second half.
But City equalised with 10 minutes to go through another spectacular strike from John Stones.
Haaland then completed the turnaround four minutes later, directing Joao Cancelo’s superb outside-of-the-boot cross past Dortmund goalkeeper Alexander Meyer.
At full-time, the cameras captured former Dortmund teammates Haaland and Bellingham holding a brief conversation on the pitch at the Etihad.
In a clip circulating on social media, Bellingham appears to mouth the phrase “f***’s sake mate” at Haaland, in apparent disbelief at the striker’s incredible winner.
Haaland has now scored 13 goals in just nine appearances since joining City in a £51m move from Dortmund in the summer.
The 22-year-old has also managed 26 goals in just 22 appearances in the Champions League.
Speaking after the match, Bellingham was full of praise for his former teammate.
“That shows his quality,” Bellingham told BT Sport.
“He’s not always in the game but you know that you give him half a sniff and he can make a goal.
“That’s what he did tonight.”
Victory for City moves them three points clear of Dortmund at the top of Group G.
Pep Guardiola’s side next face Wolves away from home on Saturday, while Dortmund face bitter rivals Schalke in the Bundesliga on the same day.