Misbah scored an unbeaten 53 off 43 balls after Pakistan's target was revised to 189 in 31 overs when more than an hour of play was lost due to rain. Samuels smashed nine fours and four sixes to steer West Indies to 261-7.
Misbah hit three fours and a six and added a match-winning 72 runs for the third wicket with Mohammad Hafeez, who hit 59. Pakistan leads 2-1 in the five-match series. The last game is on Wednesday.