PNG took a 1-0 lead after the 8th minute of play when Patrick Aisa powered a kick into the nets.
PNG held on to the lead going into half time.
Fiji came out stronger in the second half and dominated possession early on in the game.
This resulted in the equalizer in the 53rd minute through Tony Tuivuna.
The game looked to be going towards a draw with three minutes extra time given.
A header from Captain Alwin Komolong off a PNG corner kick in the dying minutes of extra time sealed the game before an estimated crowd of about four thousand.
In the gold medal play off later tonight at 7pm, New Caledonia takes on Tahiti.