Gayle smashed 116 from just 67 balls in an innings that included seven fours and 10 sixes. He shared a 162-run stand with Chadwick Walton, who scored 76 off just 36 balls.
However, hosts St. Kitts came out all guns blazing in the second innings. Openers Evin Lewis and Devon Thomas took them past the 80-run mark in the first five overs. Lewis scored 53 off just 18 balls in an innings that included six sixes and three fours.
After the fall of the openers, Laurie Evans and Fabian Allen continued the assault. The pair put up 76 runs between them in just 40 balls. Allen kept his calm despite St Kitts losing three wickets within two overs between the 10th and 15th overs. He then found an able partner in Shamarh Brooks, and by the time the latter was dismised in the penultimate over by Andre Russell, St. Kitts needed just 15 to win off 11 balls.
Campbell ticked off the deficit in that over itself with a six and two fours off the last two balls.