Glamorgan 181 for 7 (Rudolph 77, Berg 3-34) beat Hampshire 158 for 6 (Carberry 70) by 23 runs
Jacques Rudolph hit a splendid 77 as Glamorgan leapfrogged Hampshire into the NatWest T20 Blast South Group qualification positions.
Former Test star Rudolph scored his third half-century in the competition as the visitors returned to Wales with two points.
The Southampton setback completed a bad week for Hampshire who were annihilated at Essex last Friday and outclassed at Lord's by Middlesex in the LV= County Championship.
The 23-run defeat was Hampshire's fifth in a row across the formats and a sixth finals day in succession looks more and more unlikely.
After winning the toss and batting, Rudolph started as he meant to go on with a sumptuous cover drive and a swipe through the off side for two early boundaries.
The opening maximum of the night came from birthday boy Colin Ingram who hit over the covers to the minuscule boundary before offering Vince a steepling catch to give the home side the breakthrough.
South African Rudolph reverse-swept a firm four to reach the end of the powerplay 54 for two, before a flurry of wickets.
Jackson Bird flew to his left to pluck a Ben Wright drive out of the air and then Chris Cooke pushed straight to Jimmy Adams at backward point to give Danny Briggs his first of the night.
Amongst the wickets, Rudolph brought up his half-century with a powerful sweep and a single off 30 balls.
Briggs was the pick of the Hampshire bowlers, ending with figures of 2 for 13 and picking up his second wicket of the evening as David Lloyd picked out Chris Wood.
Mark Wallace forced a stunning catch from wicketkeeping counterpart Adam Wheater after striking a rapid 21 from 14 before Rudolph produced the shot of the night with a switch-hit but two balls later Wood found a top edge before a second incredible Wheater claim.
Glamorgan accelerated towards the close as Craig Meschede smashed 35 off 17 balls, including four sixes, to reach 181 from their 20 overs.
Hampshire began their first chase of the season at the Ageas Bowl in sluggish style before Michael Carberry lofted the first six of the innings over the covers in the third over.
Carberry and opening partner James Vince began an onslaught on the Glamorgan attack, the former collecting a trio of boundaries off Michael Hogan.
Just as the pair were ticking Vince chipped to Andrew Salter to depart for 28 and end a quality opening stand of 69 for the biggest partnership of the night.
Carberry smacked his second maximum into the back row of the stand to a grateful fan - which brought up a 31-ball 50, his 25th half-century in this format.
Adams and Owais Shah both swung across the line to fall identically leg before wicket for five as Hampshire stuttered, then Carberry fell trying to slog Ruaidhri Smith out of the park for a 45-ball 70.
The home side's crumble continued as Will Smith hit straight to Hogan before Wheater holed out to end the contest.