Cardiff led 15-8 at half-time but disintegrated in a second period in which they rarely crossed the halfway line.
Ulster, dominant up front throughout, began to string a few passes together to claim their first Magners League win on the road since September.
In the early stages, the understrength Blues displayed a refreshing willingness to throw the ball around. A well-timed pass from fly-half Ceri Sweeney sent full-back Chris Czekaj away and winger Tom James collected a loose kick to race clear before being brought down just short of the try-line.
A Cardiff try duly arrived when New Zealander Casey Laulala picked up a blocked Ulster clearance before skipping past two defenders to score and Sweeney added the conversion.
Ulster hit back, making ground down the left before spreading it right for teenage winger Craig Gilroy to cross with a spare man outside him.
A long range penalty from fly-half Ian Humphreys put Ulster ahead at 8-7 and the Blues suffered a setback when they lost influential number 8 Xavier Rush through injury.
A deliberate knock on, which prevented Czekaj from setting up James for a try, saw a yellow card produced for Ulster full-back Adam D'Arcy.
While D'Arcy was off the pitch, James claimed his deserved touchdown after hooker Rhys Thomas and flanker Michael Paterson had been held up close to the whitewash.
Sweeney slotted a penalty after the visitors' Chris Henry was also found guilty of a deliberate knock on. With Ulster losing their South African captain Johann Muller to injury, it looked like an uphill task for the men in white.
But everything changed in the second half as the visitors bolstered their line-up in the shape of Ireland internationals Andrew Trimble and Paddy Wallace and, with D'Arcy restored to the action, they began to look more dangerous.
Cardiff could have gone further ahead, only for Paterson's failure to hold onto a try-scoring pass from James.
Instead, Humphreys narrowed the gap with a penalty and then dinked a kick ahead which the lively Gilroy retrieved before slicing past two defenders on his way to the posts.
D'Arcy powered down the left winger to notch a well-taken try, straight off the restart, and there was a totally different complexion on the game.
Replacement flanker Willie Faloon then galloped through to clinch the bonus point for Ulster, with the home defence cut to ribbons.
There was even more misery for the Blues when hooker Gareth Williams miscued a grubber kick and Wallace was able to go over unchallenged for the fifth try. Humphreys' third successful conversion completed a much-needed win for the Ulstermen.
|Cardiff Blues Score Card|
|Ulster Rugby Score Card|