Goals from Kenny McLean and Sam Parkin either side of half-time gave the Buddies their first win of the season, and with Dundee United, Hearts and Celtic not in action the result was enough to put St Mirren top with four points.
Saturday's other SPL clashes all ended in draws. Inverness were held 1-1 by Kilmarnock, Motherwell and St Johnstone drew 1-1 and Aberdeen's clash with Ross County finished goalless.
- Dundee United
- Sam Parkin
- Kenny McLean