When the score was 64 for two after 14 overs, rain intervened losing close to 2 hours and 15 minutes play and when the action began, New Zealand were set a revised target of 151 off 25 overs, which meant they needed 87 more to win off the final 11 overs.
That gave Pakistan a total to defend and their hopes were raised when Munro was out in the frist over and Williamson (19) fell to a brilliant catch by Shadab off Faheem Ashraf.
Imam-ul-Haq, in for the injured Fakhar Zaman, was out for two in the fourth over and Azhar Ali followed five balls later for six.
But just as in the first ODI in Wellington on Saturday, the Pakistan top order were not allowed to settle.
Mohammad Hafeez anchored Pakistan's innings with 60 from 71. Speaking to the media after the loss, Shadab Khan expressed his disappointment.
Earlier, a spirited fightback from Hasan and Shadab helped Pakistan to a respectable 246 for 9 despite being reduced to 141 for 7 at one stage. However, Guptill and Ross Taylor (45 n o, 43b, 4×4) ensured victory for the hosts comfortably.
Tim Southee (2-57) and Trent Boult (1-54) both claimed early wickets to give the bowling side the upper hand. They managed to do it in style with Martin Guptill unleashing a fantastic session of pinch-hitting in the middle.
Hasan survived a blow on the chin from a fierce Lockie Ferguson delivery to reach his maiden half century remarkable, while Shadab capped off a superb day's work by taking a ripper of a catch to dismiss Williamson.
Pakistani skipper Sarfraz Ahmed will be looking towards the senior players to take responsibility and lift the team. Tim Southee got the wicket in nearly identical fashion to the first ODI, Azhar falling over to off stump and missing a straight one that thudded into his pads. "I thought for the first half the guys were brilliant with the ball and then Pakistan showed some real resistance at the end and put some partnerships together to get what could have been a tricky little total on that surface".
Guptill was named Man of the Match, and said: "We got off to a good start".