St Mirren remain in the top-flight with Marcus Fraser's second-half goal was enough to secure the Buddies status as a William Hill Premiership club.
The defender netted the only goal of the game on 65 minutes to give Craig McLeish's side a 1-0 victory and a 2-1 aggregate win over Partick Thistle in the Play-Offs.
The interim boss made two changes to the side that drew 1-1 with Thistle on Thursday night. That saw Jayden Richardson and Jake Young come in from the start in place of Richard King and Mark O'Hara.
It was Fraser who had the first opportunity of the match when he got his head on the end of Jacob Devaney cross, but his effort was routine for Josh Clarke in the Thistle goal.
The was a nervousness about Saints in the opening stages. Robbie Crawford headed on 10 minutes before Aidan Fitzpatrick curled a free-kick wide three minutes later. It took the Buddies until the latter stages of the half to really get into the match. Killian Phillips slipped the ball through to Mikael Mandron who dragged an effort wide from 20 yards on 39 minutes. Two minutes later it was Mandron who teed up Phillips inside the area. The Irishman turned inside the box to get his shot away but it deflected harmlessly into the arms of Clarke.
Saints started the second-half brightly and a powerful strike from Young 25 yards from goal forced a terrific save from Clarke who was at full stretch to touch over. From the resulting Scott Tanser corner, Fraser saw a header cleared off the line by Tony Watt. Ross Sinclair was forced into action on 54 minutes when he made a brilliant stop to push away Alex Samuel's strike.
McLeish made his first substitutions a little after the hour mark with the introduction of captain Mark O'Hara and Roland Idowu in place of Allan Campbell and Young. O'Hara's impact was almost instant as he set up the goal that would ultimately secure our place in the top flight next season. The skipper swung a free-kick deep to the back post where Fraser was sliding to knock it home off the underside of the bar with what was a wonderful finish. There was an agonising wait as VAR checked for an offside, but the lines were drawn and it was shown to be onside.
There would be no hopes of a nice easy finish to the match as Thistle looked to level the tie. Sinclair made a stunning save with just over 10 minutes remain to push away a thunderbolt from substitute Logan Chalmers. The away side would have one final chance to take the game to extra-time when they won a free-kick on the edge of the area in the final minute of added on time. Kyle Turner stepped up but could only send it into the wall. That allowed Tanser to lash clear and the SMiSA Stadium erupted as Nick Walsh blew his full-time whistle to ensure we remain in the top division heading into our 150th anniversary.
Full-Time: St Mirren 1-0 Partick Thistle
St Mirren: Sinclair, Fraser (c), Gogic, Freckleton, Richardson (King 85), Phillips, Devaney, Campbell (O'Hara 62), Tanser, Young (Idowu 62), Mandron
Subs: Tamosevicius, McMenamin, Falconer, Calvin, Nlundulu, Douglas
Partick Thistle: Clarke, McBeth (Chalmers 66), Ashcroft, Loughrey, McPherson (Logan 46), Crawford (Turner 82), Stanway (Lets'osa 75), Reading (Mackay-Steven 75), Fitzpatrick, Samuel, Watt
Subs: Budinauckas, M.Falconer, Dolan
Referee: Nick Walsh
AR1: Daniel McFarlane
AR2: Calum Spence
Fourth Official: Duncan Nicolson
VAR: John Beaton
