Papua New Guinea's middle order delivered as the Barramundis chased down 274 runs to beat Namibia by five wickets in the first of two one day matches in Port Moresby.
The visitors posted an imposing 273 for 4 batting first at Amini Park.
Craig Williams struck an impressive 109 not out from just 89 deliveries, including seven fours and five sixes, while Wian van Vuuren made a half century at the top of the order.
Four bowlers managed one wicket each, with Mahura Dai conceding just 24 runs from his ten overs.
The Barramundis run chase began badly with openers Vani Morea and Tony Ura dismissed in the first five overs.
Lega Siaka stabilised the innings with 70 from just 78 balls before Sese and Dogodo Bau combined for a match-defining 126 run partnership for the fifth wicket.
Sese Bau compiled 76 runs before being dismissed with PNG only nine runs shy of victory.
Dogodo Bau earned man of the match honours on his limited overs debut, finishing 80 not out from 74 balls, as PNG reached their target with two overs to spare.
The teams return to Amini Park tomorrow (Sunday) for the second one dayer where a win would send Papua New Guinea to the top of the World Cricket League Championship.