Replying to the hosts' total of 242 for seven, skipper Misbah-ul-Haq's innings of 63 again piloted the visitors to their target although they made heavy weather of it at the end, Kieron Pollard missing the stumps at the non-striker's end and Saeed Ajmal dashing home for the winning run to the relief of his teammates.
Pakistan take the five-match series 3-1 with one tied and now both teams shift focus to the two Twenty20 internationals to be played on Saturday and Sunday in St Vincent
Misbah, who was dismissed at the start of the final over with the scores level, took both the man of the match and the man of the series awards. Not for the first time over the five matches, the fate of the match hinged on his contribution with the bat.
But from the West Indies standpoint, they were left to lament a controversial moment when they were convinced that the Pakistani captain was caught off the glove by stand-in wicketkeeper Lendl Simmons off a fiery Tino Best.
On 49 at the time, and with the score standing at 190 for four in the 43rd over, his dismissal then with 53 runs still needed could have been pivotal.
Umpire Paul Reiffel's not out decision was challenged by West Indies captain Dwayne Bravo but the Decision Review System (DRS) upheld the on-field verdict, much to the dismay of the Caribbean players on the field.
"A key decision went against us and that was the turning point in the game," said Bravo at the end of the match in a less-than-veiled reference to the Misbah incident. "I don't think 3-1 for Pakistan was a fair reflection of the balance of power in the series."
Ahmed Shehzad contributed a top score of 64 at the top of the order, but after being becalmed in the middle of the innings by some determined bowling from the West Indies, Misbah found an able ally in Umar Akmal, the same pair who had taken Pakistan to victory in the rain-shortened fourth match three days earlier.
They put on 66 for the fifth wicket and tilted the balance of the match decisively Pakistan's way only for Akmal to fall to a persevering Best for 37 just as an unexpected light shower swept across the ground.
A washout at that stage with the score at 226 for five off 47.4 overs would have given the tourists victory anyway for they were ahead on the Duckworth/Lewis method.
However, the skies cleared and when they resumed after 20 minutes, Pakistan just managed to get across the line despite Misbah's dismissal, the key blow being delivered by Shahid Afridi when he hoisted Bravo over square-leg for six in the penultimate over.
"We really wanted this victory to finish the series off strong after all the disappointments earlier this year," reflected a delighted Misbah.
"This was just my turn to have a really good time with the bat but it was the bowlers who kept us in these matches throughout. That really is our strength."
The loss was especially hard on Bravo who had belted 48 off just 27 balls to give his team's innings a late surge with 62 runs coming off the final five overs.
His effort, together with a quickfire 29 from Darren Sammy, was essential to get a competitive total on the board despite earlier contributions from middle-order batsman Marlon Samuels (45) and opener Johnson Charles (43).
Junaid Khan and Mohammad Irfan shared five wickets in underlining their excellent performances during the series.