New Zealand 297 for 2 (Mitchell 118*, Conway 111*) beat England 291 for 6 (Buttler 72, Malan 54, Stokes 52, Livingstone 52) by eight wickets
Cardiff: England were beaten by eight wickets as New Zealand comfortably won the opening one-day international in Cardiff.
Set an imposing 292 for victory, unbeaten centuries from Devon Conway (111* off 121 balls) and Daryl Mitchell (118* off 91 balls) saw the Black Caps home with 4.2 overs to spare.
The pair added 180 for the third wicket in a patient run chase on a slow pitch.
All-rounder Ben Stokes made 52 on his return to ODI cricket as England posted 291-6.
Opener Dawid Malan made 54, captain Jos Buttler top-scored with 72 and Liam Livingstone entertained with his 39-ball 52.
Harry Brook, who was drafted into the squad as late batting cover, opened alongside Malan in the absence of Jonny Bairstow and Jason Roy, who missed out through a shoulder injury and back spasm respectively. However, the Yorkshire batter was scratchy for his 25 from 41 balls.
But despite several contributions, none of England's batters were able to kick on in the style of the chanceless Conway, and Mitchell, who made the most of being dropped on 49.
Pace bowler Gus Atkinson, who has been named in England's provisional World Cup squad, made his ODI debut but went wicketless for 47 runs from his seven overs.
The second ODI in the four-match series is in Southampton on Sunday.