Samuels's unbeaten 100 from 99 balls with 17 fours and a six helped West Indies overhaul Pakistan's 209 all out from 49.5 overs with 15.1 overs to spare and cut the home side's lead in the five-match series to 2-1.
Samuels, 25, whose last century was scored against India at Vijayawada in 2002, in brilliant form sharing a match-winning record third wicket stand of 141 from 156 balls with Shivnarine Chanderpaul (60).
The pair helped their team recover from a shaky start when paceman Rana Naved bowled Chris Gayle (9) and trapped Lendl Simmons leg before for a duck from successive balls in his second over to leave the tourists on 11-2.
Their stand is the highest against Pakistan surpassing the previous best of 137 between Vivian Richards and Richie Richardson in Karachi in 1987.
Samuels reached his hundred by punching stand-in skipper, Abdul Razzaq to the square leg boundary in a over that yielded 14 runs. Skipper Brian Lara remained unbeaten on 13.
Pakistan was led by Razzaq in the place of the experienced batting trio of captain Inzamam-ul-Haq, Mohammad Yousuf and Younis Khan.
Inzamam is nursing a finger injury while Yousuf and Younis missed the game because of domestic problems.
West Indies were boosted by the return of the experienced Chanderpaul who missed the first three games due to a knee problem.
Jamaican Samuels, long regarded as an under-achiever, played a polished but brutal innings with a series of flowing drives and ferocious pull shots one of which sailed over long on for a huge six.
He was particularly harsh on pace bowlers Rao Iftikhar and Razzaq.
Two expensive overs from them sealed the fate of the game. In his fourth over, the 18th of the innings, the two batsmen struck Iftikhar for 21 runs including a six and two fours and than in the 21st over Razzaq was hit for 15 runs. The left-handed Chanderpaul hitt him for three consecutive fours.
Iftikhar conceded 56 in 5.5 overs and Razzaq 51 in six overs.
Earlier Yasir Hameed celebrated his recall to the side after a one-year gap with a fluent 71 runs which saw Pakistan recover from 47-4 to reach a competitive total.
Pace bowlers Daren Powell with 3-33 and Dwayne Smith with 2-29 caused the damage to the top order.
Pakistan 209 all out in 49.5 overs ( Yasir Hameed 71, Abdul Razzaq 33, Faisal Iqbal 31; Powell 3 for 33, D Smith 2 for 29, Bradshaw 1 for 43) lost to West Indies 212 for 3 in 34.5 overs ( Marlon Samuels 100 n o, Chanderpaul 60; Rana Naveed 2 for 18, Mohd Sami 1 for 37)