Brechin started the game brightly and had a couple of golden opportunities early on as Stevie Hampshires shot just inside the box was tipped round the post beautifully by Saints keeper Stevie Woods, Jamie Smith also headed over the bar when he was unmarked in the box.
St Mirrens first decent chance was on 40 minutes when Ricky Gilles knocked on for a Mark Dempsie header which was inches off target.
City retaliated but Hampshires head failed to connect with the ball from a perfect Grant Johnson cross from the left.
City finally got the breakthrough about 8 minutes into the second half when Grant Johnson scraped though the defence and Scott McCulloch stuck out a foot to flick the ball into the net.
St Mirren could have levelled on 61 minutes but a Gillies ball lacked power and was caught by keeper Davie Hay, a few minutes later Gillies shot wide of the post.
City secured the 3 points 12 minutes from time when Hampshire won the ball from McGroarty to flicked on for Smith to net from close range.
Darryl Duffy had a decent debut, and caused his marker some problems with his blistering pace. All Stats are below...