Cahill headed Wanderers in front before in-form loan star Daniel Sturridge made the points safe in the second half.
Cahill's last goal came in a 4-2 defeat at Arsenal on January 20, 2010 while ex-City youngster Sturridge now has three in three for the Trotters.
However, manager Owen Coyle must make changes for Wednesday’s FA cup replay at Wigan.
Zat Knight was stretchered off after hurting himself tackling Victor Anichebe. And Sturridge is ineligible having played and scored for Chelsea in their 7-0 third round success over Ipswich.
“I’m just delighted to be playing regular football,” said Sturridge, who thought he’d set up Stuart Holden for Bolton’s third only for an assistant’s flag to disallow the goal.
“I’m enjoying my football here and now I’m looking forward to the next game.
“The manager has instilled a lot of confidence in me.
“He’s told me to go out and play my normal game, to shoot, to dribble and just show everybody what I’m about.”
Sturridge shone in front of another ex-Bolton loanee, Arsenal’s Jack Wilshere who took an opportunity to watch his former team mates.
“Jack’s different class,” agreed Sturridge. “I spoke to him and he said it’s a good club and to see him shows the affection he still has for the club.
“We’re good friends and I’m glad he’s doing so well at Arsenal.”
It’s been an eventful time for Cahill who was booked for diving in Bolton’s defeat at Tottenham 10 days earlier.
He then won his second England cap against Denmark as a second half substitute before breaking his season’s drought against relegation-haunted Everton.
His early header was deflected past Tim Howard but he was just delighted with another three points at home after some barren away days.
“It was a good collective performance but there were good individual performances and we got the right result,” he said, with Bolton in eighth spot.
“A few results went for us on Saturday so it’s good that we capitalised.
“We’re just a point behind Sunderland now and we just have to keep our heads down and get on with our work.”
Happy manager Coyle admitted he’d love to keep Sturridge but added: “That's a discussion for May.
“Chelsea certainly have some of the world’s finest strikers and Daniel, I believe, can really push himself into that category if he continues to develop.
“He looks as if he’s enjoying himself when he’s playing.
“He lights the stadium up when he receives the ball because you think something exciting is going to happen.”