Williamson silenced his critics after a recent lean spell in the shortest form of the game, scoring 72 from 46 balls as New Zealand finished on 196 for five from their 20 overs.
Guptill contributed 65 from 40 deliveries and there was a useful cameo from debutant Mark Chapman, with the former Hong Kong international scoring 20 off 13.
England’s stand-in captain Jos Buttler put the hosts in to bat after winning the toss, hoping a mottled-looking drop-in pitch with huge bald patches would prove unplayable.
But the gamble backfired as the wicket held up and New Zealand’s batsmen finally hit their stride after three straight T20 losses.
England will need to rediscover their own batting form to prevail against the Black Caps after losing to Australia twice in their opening matches of the series.
Adil Rashid was the best of England’s bowlers, taking two for 36 in his four overs, while paceman Mark Wood picked up two for 51.