Shahid Afridi fell for 7, but Umar Akamal (29 not out) and Misbah added 45 for Pakistan to cruise home with an over to spare.
"It was like a normal T20 game. Hafeez and I wanted to play normal cricketing shots," Misbah said. "It was the case of not panicking.... and the team will gain from the momentum today."
West Indies captain Dwayne Bravo, who was hit for three successive boundaries by Akmal in the 30th over, had to rely on himself as his main bowlers had already bowled five overs before the rain came. He proved costly, giving away 49 runs in his six overs for the sole wicket of Hafeez.
"I could have done a lot better. It was always us against a very good batting line-up," Bravo said. "We wanted to bat first anyway, and Marlon batted through for us today."
Earlier, Samuels smashed a brilliant 106 not out off 104 balls and featured in two productive stands adding 95 off 89 balls with Lendl Simmons (46) for the fifth wicket after putting on 57 with Chris Gayle (30), who was dropped on zero when Hafeez. Gayle was dropped down to No. 5 after previous scores of 1, 1 and 8.
Samuels answered in style to those who criticized him for facing too many balls in the past three games, scoring his fifth ODI century and second against Pakistan. He ended the innings with a six over mid-wicket off Mohammad Irfan, who claimed 2-60.