An unbeaten 59 runs from Nou Reva Rarua, plus knocks from Igo John Mahuru (31), Heagi Ronald Toua (30) and Ovia Lohia Sam (29) help set up a target of 264.
Fiji’s run chase ended inside 16 overs after they were all bowled out for 54.
Sam (4/2) made light work of the Fijians ripping through the batting attack. Sam was assisted by Boge Daniel Arua (2/23) and James Junior Tau (1/10).
Fiji: 54 16.3/50 ov RR: 3.27
Papua New Guinea: 264/9 50/50 ov RR: 5.28.
The Garamuts will take on Samoa on Monday August 14.