A late brace from Roy Krishna secured Wellington their fifth victory of the season and saw them surge to within a point of the competition's top four.
It also means the Phoenix can set a new club record of eight unbeaten games if they avoid defeat against cellar-dwellers Central Coast at home on Saturday.
Wellington's new Irish striker Cillian Sheridan made himself an instant hero, arriving impressively off the bench as a second-half substitute to tee up Krishna for what looked to be the winning goal after 82 minutes.
And Sheridan was also involved in the winner, back-heeling cleverly into the path of fellow replacement Max Burgess whose near post cross was gleefully headed home by Krishna to secure the Phoenix all three points.
Sheridan was introduced for David Williams after 63 minutes and immediately showed some nice touches, including a tracer bullet which flew narrowly over the crossbar.
With the contest locked at 1-1 heading into its final 10 minutes, the towering Irishman turned nimbly away from his marker on halfway before threading a pinpoint pass into the path of the rampaging Krishna who beat the advancing Vedran Janjetovic and scored from a narrow angle to give Phoenix a 2-1 lead.
But the Wanderers, staring down the barrel of what eventually became a fourth straight home defeat, regrouped to find an immediate equaliser – their second of the game – through Keanu Baccus, before Krishna's late winner.
The first two goals in a fiercely contested and at times niggly encounter came from unlikely sources in a six-minute period just before halftime with Louis Fenton's opener for the Phoenix cancelled out by a headed equaliser from Wanderers skipper Brendan Hamill.
The Phoenix dodged a bullet after 15 minutes when a penalty awarded against Fenton was overturned by the Video Assistant Referee. Wanderers attacker Bruce Kamau drove into the penalty area, going down under challenge from Fenton and while referee Jonathan Barreiro initially pointed to the spot, the VAR intervened to Wellington's advantage.
Fenton's opening goal came on 36 minutes when he cut in from the right, evaded some half-hearted attempts to dispossess him, received an exquisite return pass from Sarpreet Singh and planted the ball past Janjetovic. It was Fenton's second goal in the last four games of what is quickly becoming his best season in a Phoenix shirt. But the lead lasted just six minutes with Hamill nodding home a left-wing corner to square the ledger at halftime.
The home side was dealt a blow after just five minutes with outstanding German midfielder Alex Baumjohann forced off with a hamstring strain. Before halftime they'd also lost marquee striker Oriol Riera to injury.
Phoenix coach Mark Rudan made one enforced change to his side with Polish midfielder Michal Kopczynski replacing the suspended Mandi. A yellow card to Mandi's regular engine-room partner Alex Rufer will see also see him miss Saturday's match, meaning Rudan will need an entirely new midfield combination for that game.
Even so, his side will return home full of confidence after a performance which spoke volumes about the side they have become this season.
Wellington Phoenix 3 (Fenton, Krishna 2)
Western Sydney Wanderers 2 (Hamill, Baccus)
HT: 1-1
