Phillips smashed an unbeaten 106 off 74 balls, including six boundaries and seven sixes, at a newly renovated Gaddafi Stadium in Lahore on Saturday.
The No.6 propelled New Zealand to 6-330 in their 50 overs on a flat wicket with Daryl Mitchell (81) and Kane Williamson (58) also getting the feel of the wickets for the upcoming Trophy with half-centuries.
In reply, Fakhar Zaman, playing his first international in more than seven months because of illness, made a belligerent 84 off 69 - but the rest of the top-order batters struggled against spin as Pakistan were bowled out for 252 in 47.5 overs.
Phillips capped a perfect day by trapping Zaman leg before wicket with his off-spin and also took a brilliant diving catch to dismiss Babar Azam early in Pakistan's run chase.
Babar struggled in his new role as opener in ODIs for the first time since 2015 and scored a painstaking 10 off 23 balls.
New Zealand captain Mitchell Santner (3-41) clipped the top-order with his left-arm spin while Bracewell took 2-41. Fast bowler Matt Henry chipped in with 3-55.
New Zealand, already sweating on the fitness of fast bowler Lockie Ferguson, had another injury scare when the ball hit Rachin Ravindra in the face as he misjudged a catch of Khushdil Shah in the outfield and had to leave the field.
Phillips unleashed his power-hitting against Pakistan's two premier fast bowlers – Shaheen Shah Afridi and Naseem Shah -- in the last five overs that cost the home team 84 runs.
Pakistan, who lost the toss, had kept New Zealand in check at 5-246 before Phillips cut loose.
Williamson, playing his first ODI since November 2023, took his time to settle down. He reached the slowest ODI half-century in 82 balls before he edged Afridi after sharing a 95-run stand with Mitchell.
Mitchell survived a close run-out at the non-striker's end before he had scored when Babar missed the stumps from close range, but settled in well to score nearly a run-a-ball before chipping a catch to midwicket.
Pakistan also suffered an injury blow when Haris Rauf (1-23) had to leave the field due to side strain after he fell in his follow-through during his seventh over. He took no further part in the match.
Phillips smashed three sixes against Agha, who filled in for Rauf, and then hit an audacious reverse scoop against Afridi which went for a flat six over third man.
He reached his hundred in an expensive 25-run last over of Afridi, who ended up with 3-88 in 10 overs, while Michael Bracewell hit 31 in 23 balls.
Lahore hosts the second game of the tri-nation series between South Africa and New Zealand on Monday.
