The game was cut to 34 overs each side, as England fell to 55-5 after being put in to bat.
However, Liam Livingstone’s unbeaten 95 from 78 balls, part of a 112-run seventh-wicket partnership with Sam Curran, helped them rebound to 226-7.
Reece Topley then collected 3-27 as New Zealand was bowled out for 147.
Trent Boult, who had not played an ODI in over a year, made an instant effect, reducing England to 8-3 as Jonny Bairstow, Joe Root, and Ben Stokes scored only seven runs between them.
After a brief middle-order resurgence led by Jos Buttler and Moeen Ali, Livingstone and Curran, who struck 42, set a dangerous total.
England’s bowlers got off to a flying start, with David Willey dismissing the lively Finn Allen with the first ball of the Black Caps’ innings.
Mitchell’s tenacity kept them in the game during a controlled start to the chase, but England kept the pressure on throughout, and New Zealand lost their final six wickets for only 36 runs.
The four-match series begins on Wednesday at The Kia Oval.
Relive England’s crushing victory over New Zealand.
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Livingstone’s adaptability saves England.
After missing the series opener at Cardiff on Friday, Boult was primed to pounce as New Zealand sent England in to bat in bowler-friendly conditions.
And it only took him seven balls to strike, removing Bairstow in his second over with the aid of a leaping Mitchell Santner at cover, before pinning Root lbw two balls later and catching a disgruntled Stokes at mid-off in the fifth.
Boult bowled superbly, assisted by the frugal Matt Henry, who knocked Harry Brook for two, while Livingstone delivered a more controlled effort after his thrilling 39-ball half-century at Cardiff.
After the early wickets, England reshuffled the batting order, dropping Livingstone to seven from five, and he batted well to add 48 for the sixth wicket with Moeen before capitalizing late in the innings alongside Curran.
Curran, playing at number eight, too shown crucial batting talent, finally retiring for 42 from 35 balls as New Zealand failed to match England’s depth in their lineup.
Mitchell and Devon Conway both hit centuries in the first ODI, thus their middle order was not put to the test.
While the former batted calmly for another half-century, he was placed under strain by a lack of partners at the other end and ultimately holed out off Moeen, forcing a stalling run-rate.
Topley is driving increased bowling performance.
England’s bowlers struggled to generate any potency on a sluggish Cardiff wicket, but they rallied back with a brilliant all-round effort headed by Topley.
Willey was back to his swinging ball best, nipping one past Allen’s defenses in the opening over and also expertly running out Will Young from mid-off for 33.
Gus Atkinson claimed his first ODI wicket, catching and bowling opener Conway for 14, before Topley followed Livingstone in pleading for a place in England’s World Cup starting XI.
Topley bowled with remarkable consistency and found some additional bounce with his height to hamper the Black Caps’ hitters, much like Liam Plunkett, England’s middle-overs specialist who played a critical role in their 2019 success.
Topley held on to a brilliant catch in his follow-through to dismiss the aggressive Glenn Phillips for two runs, and Rachin Ravindra was caught at slip.
After a bad performance in the first ODI, he made the most of his opportunity in the second and provided encouraging signals for England’s bowling depth as they triumphed despite the absence of their important player, Adil Rashid, who was suffering from slight calf tightness.
Mark Wood’s pace has yet to appear in this series, but Atkinson appears poised to be a good deputy, while the left-arm seam of Willey, Curran, and Topley provides Buttler an enviable amount of choices.
“I am overjoyed,” Buttler added. “From the position we found ourselves in, scoring was a testament to the way we wanted to play.” Livingstone and Curran’s collaboration was amazing.
“We had to figure out how to get them off their lengths.” This team has a reputation for playing positively. We’re trying to get back into an ODI mentality since some of the players haven’t played in a while.
“Everyone on the squad is quite clear on their alternatives. We had terrific batting depth today, which was critical. Livingstone and Curran have earned the right to bat higher in the order. We’re thrilled to have completed the series.
“Willey and Topley were outstanding. We discussed increasing our powerplay bowling the other day. We were really good with the ball throughout the innings.”
