A late, stunning strike from Andy Mitchell earned Larne all three points on their travels at Mourneview Park.
In what was a hard fought and deserved victory, Mitchell stepped up to hammer home the winner from 25 yards, with 11 minutes left on the clock.
The game was a keenly contested one throughout, with Larne creating the better of the goalscoring opportunities.
The first half was a tight affair, but there were chances at both ends. The first fell to Andy Waterworth, after just six minutes. Waterworth got in behind the defence after Cian Bolger’s misjudgement, but the veteran striker fired his low effort just wide.
As the game wore on Larne became more of an attacking threat and Navid Nasseri tested Declan Brown in the home goal, before Fitzpatrick similarly went close at the other end.
The best chance of the opening half came with 34 minutes on the clock, falling the way of the visitors.
Ben Doherty whipped in a corner from the right which was nodded downwards by Bolger, with Mark Randall stabbing it just wide when well positioned.
Larne continued to push in search of the opener after the break, with Mark Haughey recovering well to deny Nasseri’s dangerous cross from the right.
On the hour mark, Randal thought he had made the breakthrough. Good work down the right saw Nasseri lay off to the former Arsenal youngster, but Brown denied him again at full stretch.
The chances were all coming the way of Tiernan Lynch’s side at this point and they were denied once more five minutes later.
Davy McDaid and Lee Lynch combined well on the edge of the box to unlock the home defence, with Lynch sent clear inside the area but some last ditch defending saw his shot turned behind for a corner, which Kofi Balmer headed just wide.
Despite Larne piling on the pressure it was almost Glenavon to got their noses in front sixteen minutes from time.
Matthew Fitzpatrick wrestled himself some space in side the box, but Balmer recovered to make the tackle and deflect the ball off the striker to safety.
The deadlock was finally broken 11 minutes from time with a stunner.
Andy Mitchell, who was doing well breaking up the play throughout the night, took a look up from 25 yards out and unleashed an effort which swerved and dipped just over Brown and into the roof of the net.
In a bid to get something out of the game home manager Gary Hamilton through Mark Stafford on as a late sub and makeshift striker.
It was another former Linfield defender who went close with two minutes left however. Michael O’Connor whipped in a corner from the right and Haughey, in space, headed well over as Larne held out for the three points.
Glenavon: Brown, Birney (’86 Stafford), Haughey, Waterworth (’86 J Doyle), Beggs (’63 Hall), Snoddy, McCloskey (’23 O’Connor), Fitzpatrick, Wallace, Garrett, Ward
Unused subs: Harmon, Doran, Hunter
Larne: Ferguson, Balmer, Nasseri, Randall, McDaid (’74 Hale), Doherty, Lynch, Mitchell, Bolger (’57 Watson), Cosgrove, Jarvis (’85 Kelly)
Unused subs: Argyrides, Oluwa, Scott, Hughes
Referee: Steven Gregg