Brian Lara's side, who were restricted to 241-9 off their 50 overs, bowled out Inzamam-ul-Haq's unpredictable Pakistanis for just 187 in 47.
2 overs at a sun-drenched and packed Sabina Park in Jamaica.
Chasing 242, Pakistan looked on track when Mohammad Yousuf and Inzamam put on 60 for the fourth wicket.
But man-of-the-match Dwayne Smith then snared three wickets - including Yousuf and Inzamam - for 36 runs from 10 overs.
Though Shoaib Malik cracked 62 to lead a late charge for the Pakistanis, Dwayne Bravo snuffed the life out of the comeback with three for 42 from nine overs.
Earlier Marlon Samuels hit 63 to lead the West Indies to a respectable score after they had struggled to 101-3 at the 30-over mark.
"Players like Marlon Samuels, Dwyane Bravo and Dwayne Smith were really special," said Lara.
"The young players showed great spirit. Marlon had a real go and got us to four an over.
Then we bowled well, it was a real team effort."
Inzamam, whose side came into t