Solid contributions by the Bravo brothers, Darren and Dwayne, boosted the West Indies batting effort after they had gotten off to the worst possible start when giant left-arm fast bowler Mohammed Irfan had Chris Gayle caught at the wicket in the first over of the day.
Two days after demolishing the hosts by 126 runs, the visitors folded for 195 off 47.5 overs in reply to the Caribbean side's total of 232 for eight after they were put in on a pitch expected to offer considerable assistance to the bowlers following the previous day's torrential rain.
Pakistan appeared to be cruising along at 103 for two with skipper Misbah-ul-Haq well entrenched and opener Nasir Jamshed (54) riding his considerable luck towards a half-century. But Misbah played a shot totally out of character to be bowled by Darren Sammy, a fitting reward for the all-rounder playing his 100th ODI.
That dismissal was followed by a succession of poor shots and with spinner Sunil Narine returning to wicket-taking form in snaring four for 26 to claim the "Man of the Match" award, a rearguard 50 by wicketkeeper-batsman Umar Akmal proved to be too little, too late for Pakistan.
With the series now level, the teams travel on to St Lucia for the remaining three matches, beginning on Friday, before the short tour concludes with two T20 matches in St Vincent on July 27 and 28.
Darren Bravo's top score of 54 paced his team through the first half of the innings while skipper Dwayne Bravo provided vital impetus in holding the latter half of the innings together with an unbeaten 43 that proved critical in helping the Caribbean side to a challenging score.
"Given the nature of the pitch, I thought 230-235 would have been a good total," said a relieved Dwayne Bravo after he completed victory with the last two wickets off consecutive deliveries.
"We really needed this win to get some confidence back and we can't forget the fans, because they are the ones who suffer the most when we play as badly as we did last Sunday."
Shahid Afridi, the undoubted star of that opening encounter, claimed two wickets, as did Saeed Ajmal, the pair of slow bowlers threatening to stifle the home team as they did so effectively two days earlier. Afridi could not replicate his heroics with the bat however, one wild swing too many bringing about his demise via a stumping.
Darren Bravo and Johnson Charles (31) counter-attacked either side of a break before rain following Gayle's swift demise, the pair putting on 79 runs for the second wicket. The runs then dried up during the middle of the innings with Bravo and Marlon Samuels struggling to get the ball away.
It took the arrival of the batting powerplay to change the complexion of the innings as wickets fell in a rush, only for Kieron Pollard (30) to finally provide some stability and acceleration with his captain, the pair taking the West Indies from the uncertainty of 150 for five in the 39th over to 220 when Pollard was bowled by Asad Ali in the penultimate over.
"Our bowlers didn't use the moisture in the pitch well," said Misbah in the aftermath of defeat. "The pitch then got slower and lower so it made life really difficult for us when we batted. We didn't help our cause by some bad shots."
Conditions are expected to be more batsman friendly when battle is resumed at the Beausejour Stadium in what is effectively now a best-of-three contest.