Morton won to overtake opponents Raith Rovers and move up to third in the table.
Raith's Stuart Anderson tested goalkeeper Derek Gaston and Scott Taggart's long-range drive sailed wide of the visiting goal in the first half.
Stephen Stirling's thunderous 25-yard strike broke the deadlock midway through the second half.
Simon Mensing headed over and Jason Thomson fired wide as Raith chased an equaliser.
Gaston, Taggart, Reid, Mark McLaughlin, Dyer, Stirling, Bachirou, Tidser, Graham, Weatherson, Campbell (Gormley 79). Subs Not Used: Hutton, Wallace, O'Ware, McDaid.
Taggart, Dyer, Stirling.
McGurn, Thomson, Mensing, Hill, Malowne, Smith, Stuart Anderson, Walker, Hamill (Grant Anderson 78), Brian Graham, Greig Spence. Subs Not Used: Laidlaw, Ellis, Donaldson, Callachan.
Brian Graham, Mensing, Hill.