match report courtsey of www.bbc.co.uk/nisport
Ulster secured their first bonus-point win of the season thanks to a superb second-half comeback in Cardiff.
Tries from Carlos Laulala and Tom James helped the Blues to a deserved 15-8 lead at the break with debutant Craig Gilroy going over for the visitors.
Gilroy sparked the fightback with a 58th minute touchdown and Willie Faloon, Adam D'Arcy and Paddy Wallace added further tries.
The win takes Ulster up to third and above fourth-placed Cardiff.
Both teams were under-strength with many of their top players on international duty and Cardiff dominated the early stages but had to wait until the 15th minute to register their first score.
Laulala darted through the middle and weaved his way to line for a fine individual try, with Sweeney adding the conversion.
Ulster hit back three minutes later with their first meaningful attack, a flowing move across the field ending with debutant Gilroy racing in at the corner.
Ian Humphreys failed to add the extra points but he made no mistake with a long-range penalty.
Ulster full-back Adam D'Arcy was controversially sin-binned for a deliberate knock forward on 32 minutes.
The Blues took advantage of the extra man, with Sweeney firing over a penalty to make it 10-8 before James went over for Cardiff's second try two minutes from the break.
Gilroy was caught and dispossed close to the Ulster line and Laulala's pass gave James a clear run to the line.
Sweeney was off-target with the conversion but the Blues went in with a deserved seven-point lead.
Ulster coach Brian McLaughlin brought on Ireland pair Paddy Wallace and Andrew Trimble early in the second half.
Michael Paterson's failure to hold a James pass cost Cardiff a try and the clinical finishing was soon to come from Ulster.
A Humphreys penalty cut the gap and the fly-half's kick set Gilroy on his way to his second try on 58 minutes, the young wing storming past two defenders before going under the post for a converted touchdown.
Two minutes later and a complete turn-a-round in the game, with D'Arcy sprinting clear down the left wing and going over in the corner.
Humphreys missed the conversion and a subsequent penalty but Ulster were now eight points ahead.
Faloon secured the bonus point with nine minutes left when he burst through for a converted try after a fine pass from Paul Marshall.
Wallace ran clear to the line after a Blues mistake for Ulster's fifth try and Humphreys complete the victory with the conversion.
|Cardiff Blues Score Card|
|Ulster Rugby Score Card|