Former Walsall loan midfielder Peter Sweeney helped Bury to a deserved win over his old club at Bescot.
Sweeney's early left-foot 30-yarder flew in off the underside of the bar.
Jon Macken then levelled from the spot on 28 minutes after Shane Byrne tripped Jamie Paterson in the box.
But Michael Jones cut in from the left to restore Bury's lead straight after the break, Steve Schumacher and sub Lenell John-Lewis also netting before George Bowerman's late consolation.
That was the teenager's first senior goal for relegation-threatened Walsall.
At the final whistle, players had to separate Walsall defender Manny Smith and Bury sub David Worrall after the pair squared up to each other.
Sweeney, who played seven games on loan with the Saddlers three years ago, also had a hand in two of his side's other three goals.
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Bury manager Richie Barker told BBC Radio Manchester:
"We were excellent, and the performance in the second-half was absolutely fantastic.
"Peter Sweeney with his left foot doesn't score enough goals, he should be scoring like that on a regular basis.
"As a manager I think you get judged on your signings and your results, so it's important for me that my signings are successful."