Cronje took two wickets in the West Indian score of 245 and then scored 61 not out to steer South Africa out of trouble and cruise home with 18 balls to spare.
The South Africans, boosted by opener Mike Rindel's 49, were comfortably placed at 118-2 when three wickets fell for 19 runs to make it 137-5 in the 27th over.
A composed Cronje added 74 for the sixth wicket with Dale Birkenstein and 37 for the unbroken seventh with Derek Crookes, who hastened the end with a brisk 24 off 21 balls.
It was South Africa's second title in as many months, having won the first-ever cricket gold at the Commonwealth Games in Malaysia in September under stand-in captain Shaun Pollock.
Jacques Kallis set up South Africa's win with a career-best 5-30 after pugnacious opener Philo Wallace threatened to take the match away with a maiden one-day century.
Wallace belted 10 boundaries and five sixes in a run-a-ball 103 after South Africa sent the West Indies to bat in overcast conditions.
Carl Hooper's 49 was the only other major contribution as Kallis sliced through the lower order to bowl the West Indies out with three balls still remaining.
The West Indians, sailing comfortably at 180-3, lost their last seven wickets for 65. The irrepressible Jonty Rhodes took three catches after failing to hold two difficult chances offered by Wallace early in his innings.
"It feels good to win this tough tournament," said Cronje after receiving the winner's purse of 100,000 dollars.
"There were no second chances in this knock-out format, so I think we did well to play three good matches.
"We knew we were among the top there, but this has renewed our confidence for next year's World Cup."
West Indian captain Brian Lara, whose team begins it's first-ever tour of South Africa later this month, was not unduly disappointed.
"Not many expected us to reach the final but we showed we were good enough for that," he said.
"I am happy the boys fought till the end, it was a very close game. It's all about taking your chances and the South Africans took theirs well and deserved to win."
Lara said he was looking forward to the South African tour, saying his team "was determined to make the West Indian people proud of it."
Date-stamped : 01 Nov1998 - 16:33