Shamar Apple struck a half-century while Rivaldo Pereira claimed five wickets as Guyana pulled off a 14-run win over Jamaica in Antigua.
Jamaica looked good chasing the 200-plus run target, led by Tyson Gordon 57 and Demario Hall who scored 52 with but failed to carry their team over the line.
Guyana churned out yet another brilliant spell of bowling with Ravaldo Pereira (5-29), Danvir Seegobin (2-27) and captain Adrian Hetmyer (2-49), keeping Jamaica to 205 all out 48.4 overs.
Earlier, Guyana made 219 all out in 48 overs, after a brilliant knock from all-rounder Apple, who cracked four sixes with a pair of fours to lead with 65 off 69 balls.
Khush Seegobin stroked 46, while Hetmyer (24) and Emmanuel Lewis (16) were among the main scorers for Guyana.
Jamaica used six bowlers with Ryan Lyttleton (4-53) leading the attack. Hall returned to grab 2-29 while 4 others grabbed a wicket apiece.
Guyana will play Windward Islands in round four on April 1.