Striker Darren Murray scored twice as Portadown secured victory in Tuesday's Mid-Ulster derby at Mourneview Park.
Murray swivelled to fire in the opener on 42 minutes after Ross Redman's corner from the right was not cleared.
Defender Gary Breen headed in from another Redman corner for 2-0 and Murray netted the third after keeper Andy Coleman had saved from Gary Twigg.
Glenavon rallied late in the game and Mark Farren stooped to score from a cross by Guy Bates.
The Lurgan made other chances late on but Ronnie McFall's Ports had done enough to claim the victory.