St Johnstone ended a two month winless run as Chris Kane's 13th minute goal won the battle of the Saints.
But the Buddies will rue sinner Simeon Jackson's pathetic penalty miss in the opening 10 minutes as his attempted dink trundled straight down the middle and was easily saved by Zander Clark.
The defeat leaves St Mirren rooted to the bottom of the table and running out of time if they are to save their Premiership skins.
St Johnstone though climb to seventh and still with a sniff of making it into the top six before the split in three games' time.
St Mirren had the perfect opportunity to open the scoring in the seventh minute after Brad Lyons was bundled to the ground by Jason Kerr.
Jackson took the responsibility from 12 yards. But the Canadian's attempt at a 'Panenka' was poorly executed and barely made it to the goal line before being booted clear by the trailing leg of Clark.
It went from bad to worse for the Buddies just six minutes later when Kane netted for the home side. The 24-year-old showed composure when sent clear through to beat Vaclav Hladky.
The Paisley side pushed for a leveller in the second period but never seriously tested Clark.
And their woes were complete two minutes from time when Ethan Erhahon shown a straight red for lunging tackle on Richard Foster.
