The Irish province were ruthless as they raced into a 21-3 lead in the Welsh capital, leaving the Blues with a huge mountain to climb.
Kristian Dacey powered over in the closing stages of the half but despite dominating large periods after the break the Blues battled with little reward.
Ulster struck against the run of play to wrap up the bonus-point before the Blues threatened a comeback with tries from Willis Halaholo and Alex Cuthbert.
But Darren Cave claimed a late try to secure the visitors’ victory and deny the Blues a losing bonus-point.
The Blues were forced to make two late changes in the hours before kick-off with Sam Warburton and Jarrad Hoeata the latest victims of a bug going around the camp.
James Down came straight into the starting line-up with Josh Turnbull moving to the back-row and Shane Lewis-Hughes onto the bench.
But they made an impressive start and Steve Shingler knocked over an early penalty to take the lead.
Both Tom James and Rey Lee-Lo were promising, with breaks in the early exchanges, but the Blues were unable to make more from the half chances.
Ulster took the lead on 25 minutes thanks to full-back Charles Piutau but it was Ruan Pienaar that did the damage.
The scrum-half dummied his way through from a set move and came within inches of scoring. Blaine Scully made the try-saving tackle but was subsequently sent to the sin-bin for failing to roll away.
Pienaar took a quick-tap from the resulting penalty and despite the Blues soaking up eight phases, the pressure eventually told.
Ulster took advantage of their superior numbers on the right with Piutau crossing. Pienaar added the conversion and he soon made it 14-3 after Stuart McCloskey took advantage of a missed tackle in mid-field.
Matters were made worse in the closing stages of the half as Lloyd Williams saw his clearance charged-down by his opposite number.
Scully scrambled to collect the ball but somehow Ulster came out with it and Kyle McCall burrowed over.
The score-line perhaps flattered Ulster, who displayed a ruthless edge, but with ball in hand the Blues looked dangerous.
They rallied in the closing stages with Alex Cuthbert and Lee-Lo particularly prominent before Kristian Dacey powered over for a crucial try in the final play.
Shingler was unable to add the extras as the Cardiff Blues went into the break trailing by 13-points.
Piutau set alarm bells ringing early in the second half but the Blues survived and were soon on the attack.
A beautiful slight of hands from Willis Halaholo released Blaine Scully and the ball was worked to Cuthbert. The wing raced to the corner but was taken out by a high tackle. Iain Henderson was sent to the sin-bin but referee Andrew Brace awarded only a penalty and not a penalty try due to the cover defence.
Cardiff kicked to the corner and after the ball came loose it looked as though Lloyd Williams had sniped over but he was unable to ground the ball.
The Blues kicked two more penalties to the corner in the following minutes but were unable to cross for the crucial try, despite rumbling over the line on the second occasion.
Ulster continued to give away penalties, as they frustrated the Blues, and soon saw Luke Marshall shown yellow after cynically coming in from the side.
But the Northern Irish province were far more clinical with their chances and after the ball was lost in midfield they went half the pitch with Chris Henry bundling over.
Pienaar converted expertly from the touchline to open up a 20-point advantage. Danny Wilson's men refused to throw in the towel and gave themselves a glimmer of hope when a trademark Nicky Robinson pass to the left found Halaholo.
The centre had support on the left but ghosted through for a try. Robinson converted.
Robinson, who came out of retirement this week, then rolled back the years as he sliced through the Ulster defence to send Alex Cuthbert over.
He converted the score to set up a tense finale but from the restart his rustiness showed as he was charged down, with Cave scoring and Pienaar converting.