The Buddies were outgunned in the battle of the Saints as the Perth side deservedly picked up the spoils.
St Johnstone spurned a host of first half chances as St Mirren struggled with an unfamiliar 3-5-2 formation, with only some excellent defending from Richard Tait and shot-stopping from Jak Alnwick keeping the sides level.
The visitors reverted to 4-4-2 just before half-time, but it failed to swing the game in their favour as the hosts finally went in front when substitute striker Stevie May slotted home a Craig Conway cross.
It took St Mirren 80 minutes to muster their first effort, Kristian Dennis lashing straight into the arms of Elliot Parish.
There was no late rally from St Mirren as they endured a disappointing afternoon before the international break kicks in.
Not only did they miss out on three points, they also lost Junior Morias and Marcus Fraser to injury.
