Andre Moritz then scored from long range in injury time for the Trotters' biggest victory of the campaign.
The result ended a five-game unbeaten run for Rovers, putting a severe dent in their play-off push.
Home manager Dougie Freedman opted not to start Alan Hutton, who signed on a month long loan deal from Aston Villa this week. He did make two changes, with Zat Knight and Neil Danns coming into the side for Matt Mills and Darren Pratley.
Meanwhile, visiting boss Gary Bowyer was without Josh King, Dickson Etuhu and Tim Cairney. But Corry Evans made his return from a four-month injury layoff off the bench.
Bolton started stronger in a typically lively opening to a derby encounter. Danns had a powerful strike tipped over the bar by Paul Robinson and then Mark Davies' shot was cleared off the line.
Blackburn hit back through Markus Ollson's curling effort from the outside of his boot. That called Adam Bogdan into action with a strong save.
However, Wanderers then took the lead that their early probing seemed to merit. Danns made himself enough space on the left flank so that he could find Kamara in the box, who then placed his header perfectly past Robinson back into the bottom left corner of the goal.
Mason missed a golden opportunity to double the lead when he was put through one-on-one with Robinson. The former England stopper saved Mason's first effort, before the on-loan striker placed his rebound excruciatingly wide.
But, shortly after, Mason made amends, producing a half-volley on the turn which caught Robinson by surprise as it nestled into the bottom left corner seconds before half-time.
Wanderers then carried through that momentum into the second half and ended the contest in controversial circumstances.
And it was Trotters captain Spearing - who was loudly jeered throughout by the visiting support - who scored it.
The former Liverpool midfielder smashed a thunderous volley from 25 yards into the underside of the bar, with the ball then bouncing down over the line and clear.
However, the game went on, with referee Paul Tierney only awarding the goal around half a minute later to the disgust of the Rovers players.
Olsson then had another opportunity to claw a goal back, but he failed to provide Blackburn with any sort of consolation, with his shot across the deck fizzing agonisingly the wrong side of the post.
Moritz then put the icing on the cake with his long-range blast beating Robinson low down to rub further salt in the visitors' wounds in the dying embers of the game.
- Sports & Recreation
- Neil Danns
- Jay Spearing
- Joe Mason
- Alan Hutton
- Zat Knight
- Aston Villa
- Dougie Freedman
- Medo Kamara