Sussex failed to capitalise on a good bowling performance, as they fell short of a chaseable target of 146 at The 1st Central County Ground.
Having won the toss and put the visitors into bat, Harrison Ward got the Sharks off to a flyer taking a wicket with the very first ball of the innings. The momentum continued in our favour and Gloucestershire found themselves on 15-3 after just 4 overs.
Gloucestershire managed to recover, with Glen Phillips and Jack Taylor putting on a partnership of 98 from 63 balls.
Obed McCoy once again showed what a valuable overseas signing he has been, taking his 13th and 14th wicket in just five T20 matches.
His last came at the death and with Gloucestershire finishing on 145 from their 20 overs, Sussex would have fancied themselves to chase them down in front of a sell-out crowd at Hove.
The chase began well, and the newly tied down Tom Alsop was in fantastic form once again, reaching 82 from just 52 deliveries to give the Sharks a great opportunity to win the game.
Alsop had good support at the other end from Fynn Hudson-Prentice, but after Tom was dismissed, the remaining wickets fell for 22 runs.
The visitors bowled tremendously well to take victory at Hove, and with a week until the next T20 Blast match, Sussex have time to regroup before making a final push to take a place in the quarter finals of the competition.