The striker came off the bench to snatch all three points in Gosford, dealing the Wanderers a blow in the race for a top-two finish
Left back Joshua Rose opened the scoring for Phil Moss’ men after 32 minutes before Nikolai Topor-Stanley’s first goal of the season eight minutes later drew the Wanderers level.
The match looked destined for draw until Ibini’s fifth goal of the season decided the contest in the 90th minute.
The result will move the Mariners to 39 points and means they will end the round at least in a share of second place.
Mile Sterjovski had the game’s first chance, hitting a shot just over the bar from 25 yards out as the Mariners looked for an opener after nine minutes.
It was then the Wanderers turn to attack with Tomi Juric looking dangerous before Aaron Mooy dragged a shot wide after a good period of play on 20 minutes.
Mooy was in the thick of the action six minutes later, pinching the ball from an Anthony Caceres throw before seeing his rasping shot tipped onto the post by Mariners goalkeeper Liam Reddy.
Against the run of play Rose opened the scoring when, after 32 minutes, he picked up the ball just inside his own half before a scything run saw him breeze through Western Sydney’s defence before sliding the ball past Ante Covic to nestle it in the right-hand corner.
The Mariners didn’t hold on for long though with Topor-Stanley equalising five minutes before the interval, tucking home a Juric pass from the right hand side of the penalty area
End-to-end attack at the Brisbane Water venue saw Sterjovski and then Mooy have chances for each side early before the Mariners had a penalty shout waved away by referee Stebre Delovski as Fitzgerald appeared to be fouled outside before falling inside the penalty area. Either way no infraction was seen by Delovski.
Three minutes after coming on as a 56th minute substitute Ibini was sent through by a well-weighted pass by Caceres but the man on-loan from Shanghai Dongya couldn’t keep his shot down.
Mooy continued to toil for the men in red and black and he provided replacement forward Brendon Santalab with a good chance in the 67th minute but the striker failed to capitalise.
The usually prolific Mitchell Duke should have scored two minutes later but he too failed to find the back of the net despite some brilliant build-up play from Simon and Kim.
Ibini and Matt Simon both worried the visitors late, but conversely the Wanderers kept Reddy on his toes when Polenz missed to the right inside the final ten minutes.
The Mariners peppered the Wanderers’s goal in the dying stages with another substitute in Nick Montgomery going close before Ibini’s winner came as he side-footed home a pass from Roux, sending the locals into delirium and secures the club finals football for yet another season.
Central Coast Mariners 2 (Rose 32, Ibini 90)
Western Sydney Wanderers 1 (Topor-Stanley 40)
Crowd: 13,157 @ Central Coast Stadiu