Pakistan wicketkeeper Umar Akmal missed a run-out opportunity and the West Indies last-wicket pair of Kemar Roach and Jason Holder scrambled two runs off the final ball to tie the third one-day international on Friday.
Responding to the tourists' total of 229 for six, and requiring 15 off the final over to win, Holder smashed a four and a six over cover off medium-pacer Wahab Riaz to keep the home side's unlikely prospects alive, resulting in the last ball drama that leaves the series level at 1-1 going into the fourth match at the same venue on Sunday.
West Indies middle-order batsman Lendl Simmons and Pakistan captain Misbah-ul-Haq, the joint top-scorers with 75 runs each in the thrilling encounter, also shared the Man of the Match award.
However, Misbah found it difficult to accept how his team could not have won the match after reducing the Caribbean side to 205 for nine in the 49th over.
"It's really, really disappointing, but I have to say the way Holder played at the end he took the game away from us," said an incredulous Misbah.
"In that last over there were too many full deliveries to the tailenders, but hats off to them, they played well."
In his usual calm, unruffled manner, Misbah had compiled his runs to steady the Pakistan innings after the early loss of both openers while Akmal swatted an unbeaten 40 off 31 deliveries, dominating an unbroken seventh-wicket partnership of 52 off 26 balls with Wahab (19 not out) to give the tourists a fighting chance on a pitch offering considerably more pace and bounce than for the first two ODIs in Guyana.
Holder and Dwayne Bravo took two wickets apiece but skipper Bravo's decision to persist with himself in the final overs proved costly, his last three overs being plastered for 40 runs.
It was a bewildering decision given that Marlon Samuels had bowled only three overs in conceding just four runs and was not utilised at the end.
"This was a match we should have won after the bowlers had done such a good job," a disappointed Bravo insisted.
"Once again the batting let us down. It should never have gotten down to the bowlers having to save us."
Pakistan's left-arm seamers made early inroads into the West Indies batting line-up and it took Simmons' effort together with a painstaking 46 from Samuels go keep the home side within reach of the target.
However, with spinner Saeed Ajmal taking three wickets in the space of two overs and Junaid Khan joining in with two scalps himself, the West Indies looked to have frittered away their opportunity in losing five wickets for 27 runs.
Big-hitting from Sunil Narine during a very brief cameo revived flagging hopes and then it came down to that decisive final over as the senior members of the Pakistan squad deliberated with their captain over who should bowl the final over.
Choosing Wahab was always going to be a gamble, as he had already conceded the most expensive over of the innings when belted for 15 runs during the batting powerplay.
Maintaining a full length gave Holder the opportunity to smash the telling boundaries after a couple of singles, leaving three runs for victory and two to tie off the final ball.
A sliced drive to third-man guaranteed at least one but he should have been run out by at least half the length of the pitch in coming back for the second tying run, only for Akmal to fail to collect the return.