The Saints had been trailing Fingal after Conan Byrne smashed in a goal on 66 minutes but Mulcahy popped up in the penalty area to head in his third goal in two games.
Saints manager Pete Mahon made two changes to the side that defeated Dundalk 3-0 in Oriel Park last week, Shane Guthrie and Brian Cash replaced by David McAllister and Gareth O’Connor, who made his debut having re-signed from Drogheda United.
Fingal boss Liam Buckley also made two changes from his line-up following their midweek Europa League defeat to CS Maritimo. Eamon Zayed replaced Shaun Maher, while Brian Gannon was a late change after Kenny Browne suffered a neck injury in the pre-match warm-up.
The home side settled quicker into the game than Fingal, Ryan Guy’s long throw-in causing Fingal problems in the penalty area, while Stuart Byrne also lashed a shot over the bar from outside the box.
The first clear-cut chance of the opening half fell to Fingal’s Ronan Finn. Lorcan Fitzgerald’s 21st minute free found the ex-UCD man free on the far post, but he couldn’t properly connect with the ball and volleyed over Gary Rogers’ crossbar.
However the Inchicore side soon took over proceedings. Firstly Guy played in Saints striker Paul Byrne, but after turning Shaun Williams, his shot could only find the side netting. The striker then volleyed a near post cross from McAllister wide just a minute later, while Derek Doyle had a goal bound shot headed clear by Fitzgerald. Moments later, Finn registered Fingal’s first effort on target but his 25 yard shot was comfortably saved by Rogers.
Scoreless at the break, Pete Mahon made a double substitution bringing Brian Cash and Danny North in for Derek Doyle and Paul Byrne. The changes appeared to aid his side’s chase for an opener, Cash heading Gareth O’Connor’s cross on goal but seeing his effort tipped around the post by Clarke. From the resulting corner, the Saints worked the ball into the box for North, whose overhead kick went just wide of goal.
Despite this pressure though, it was Fingal who took the lead. Following a foul by Damian Lynch on the halfway line, Fingal worked the ball wide to substitute Gary O’Neill, whose cut back found the onrushing Ronan Finn. The midfielder’s cross was headed towards goal by Kirby, and despite Rogers’ great reaction save, the ball fell to Conan Byrne who smashed the ball into the net from 10 yards out.
The goal forced the home side to push on even more and while Guy had a headed effort that went wide, it was Finn who would have the chance to put Fingal two ahead, but his shot was easily dealt with by Rogers.
Pat’s were denied an equaliser on 78 minutes when Dave Mulcahy’s downward header from a corner hit the crossbar and was scrambled away to safety by Fingal, the ball appearing to strike a Fingal hand in their attempt to clear the danger.
Byrne and Zayed threatened to extend Fingal’s lead on the counter attack, but it was Mulcahy who would save the day for the home side. Stuart Byrne’s high ball into the box found the onrushing Mulcahy and his header looped over Fingal keeper Brendan Clarke into the empty net.
The Saints had time to create one further opportunity to snatch the three points. However Cash’s cross from the left just evaded the outstretched foot of ex-Grimsby Town striker North, and Ryan Guy shot the loose ball into the side netting. Fingal saw out the three minutes of additional time to leave Inchicore with a point, a result which was enough for the Saints to leapfrog Shamrock Rovers in the league and into first place on goal difference.
Saint Patrick’s Athletic: Rogers, Pender, Kenna, Mulcahy, Lynch (c); Guy, O’Connor, S Byrne, McAllister, D Doyle (Cash 45); P Byrne (North 45).
Subs not used: Bennion (gk), Bermingham, Haverty.
Sporting Fingal: Clarke; O’Brien, Gannon, Williams, Fitzgerald; C Byrne (Dawson 90+1), McFaul, Finn, Kirby (Cahill 89); Zayed, Crowe (O’Neill 63).
Subs not used: Quigley (gk), Frost.
Referee: Anthony Buttimer
Attendance: 1,500 (estimate)
Extratime man of the match: Dave Mulcahy