Kerr McInroy's first-half strike ensured Shelbourne will remain champions for at least a week as they secured a 1-0 win away to Shamrock Rovers.
A point would have been enough to see Stephen Bradley’s side see off the challenge of second-placed Derry City and make it five titles from the last six.
Shelbourne have recent fortune in Tallaght too, however, as they played there for the second time in a week having designated Dublin 24 their home ground for European group games.
And they started the game with verve and on the front foot, with McInroy exchanging passes in the box with Evan Caffrey before forcing Daniel Cleary into a sturdy block.
The visitors could have led seconds later as a deep cross from James Norris found an unmarked Mipo Odubeko at the back post but, as the fans gasped, the ball ricocheted wide.
Joey O’Brien’s side continued to create the clearer openings against his former club, another Norris cross bungled over by Harry Wood before Cleary did well to nick the ball off Mipo’s toe.
With Graham Burke and player of the month Matt Healy failing to find the target for Rovers, Shelbourne had brought their shooting boots and led just past the half hour
Norris’ cross hit the hand of Cleary and, while referee Rob Hennessy played advantage, the ball fell to McInroy to fire home through a maze of bodies.
On-loan Liverpool full-back Norris continued to cause Rovers continuous problems, this time time forcing Adam Matthews to hook a cross past his own post and a scrambling Ed McGinty.
Shels continued to press after the break and a speculative McInroy effort was agilely tipped over by McGinty.
And Burke saw himself brilliantly denied by Wessel Speel as he chested the ball down in the box and sent the keeper sprawling with a well-hit low volley.
The visitors finished the final 15 minutes a man short after captain Paddy Barrett was shown a straight red card for a wild lunge on John McGovern .
And they were fortunate not to concede in the final minute as McGovern headed across goal and it was nodded off the line by sub Lewis Temple.
Then it was Speel’s turn to come to the rescue as he got down low to palm away a powerful header from Dylan Watts before a goalmouth scramble saw Watts’ backheel loop over.
But the Reds - who fly to North Macedonia to face Skopje on Thursday - held on to keep the Premier Division trophy in Drumcondra for at least one more game.
Shamrock Rovers: Ed McGinty; Adam Matthews, Daniel Cleary, Corey O’Sullivan; Darragh Nugent, Dylan Watts (John McGovern 65), Matt Healy, Danny Mandroiu, Trevor Clarke (Seán Kavanagh 65); Graham Burke, Rory Gaffney (Conor Malley 65).
Shelbourne: Wessel Speel; Milan Mbeng. Paddy Barrett, Kameron Ledwidge, James Norris; JJ Lunney, John Henry-Francis (Ali Coote 64), Kerr McIroy; Harry Wood (Lewis Temple 81), Evan Caffrey (Mark Coyle 73), Mipo Odubeko (John Martin 73).
Referee: Rob Hennessy (Limerick).
