Unbeaten in seven games at Richmond Park, Liam Buckley’s side edge level on points with fourth-placed Derry City who visit Inchicore on Friday. Sligo remain in trouble third from bottom.
Despite St Patrick’s enjoying good possession and looking threatening, it was Sligo who produced the two clear-cut chances of the first half.
The visitors defended well early on with Callum Waters deflecting a Conan Byrne shot out for a corner while captain Kyle Callan-McFadden cleared off the line.
Sligo came close to taking a 26th-minute lead. Callan-McFadden met Rhys McCabe’s corner with a firm near-post header but Barry Murphy made a brilliant save, the ball then scrambled clear.
St Patrick’s had Murphy to thank again three minutes before half-time. Adam Wixted’s clever feet worked an opening down the inside left channel with Murphy showing his agility to tip over the Sligo winger’s left-foot drive.
St Pat’s took the lead in the 51st minute. Darragh Markey and Ryan Brennan worked the ball to right-back Simon Madden on the overlap. His cross picked out Clarke at the back and the winger drilled his shot low to the corner of the net.
Conan Byrne had a shot bravely blocked while Ryan Brennan’s goal-bound header struck a team-mate as St Pat’s pressed for a second.
Home substitute Killian Brennan came close to a spectacular goal on 73 minutes as his 35-yard volley was batted away by Mitchell Beeney.
In a frantic finish, John Mahon blew a glorious chance of an 85th-minute equaliser, blazing over just yards out.
Teenager Byrne, on his first league start, then slotted home a 91st-minute spot kick for his first goal for the club to seal the win after Jake Keegan was fouled by Jack Keaney.
Murphy; Madden, Toner, Desmond, Bermingham; Lennon (K. Brennan, 60); C. Byrne, R. Brennan, Markey (Kelly, 83), Clarke (Keegan, 55); T Byrne.
Beeney; Boylan, Callan-McFadden, Mahon, Waters; Wixted (Cretaro, 80), Keaney, McCabe, McAleer (Roy, 59); Moorhouse (Morrison, 68); Morgan.
Rob Hennessy (Clare).