The Ulstermen, outplayed by a Cardiff side directed majestically by out-half Jerrod Evans, remain 13 points adrift of third-placed Edinburgh - their next opponents in 12 days' time - and while they have a game in hand over the Scottish outfit, a play-off spot now looks highly unlikely.
Indeed an upturn in results will be required to keep the ever-improving Benetton at bay and retain the chance of qualification for next year's European Rugby Champions Cup, with the Italians currently a single point behind in fifth.
Ulster welcomed two Grand Slam winners back into the fold after last week's success at Twickenham - Player of the Tournament Jacob Stockdale and Iain Henderson, coming in at left wing and blindside flanker respectively.
Elsewhere the side lined up with Charles Piutau at full-back, Craig Gilroy on the right flank, Luke Marshall and Stuart McCloskey in the centre, and the half-back partnership of John Cooney and Johnny McPhillips.
Up front Andrew Warwick, Rob Herring and Wiehahn Herbst made up the front row, with captain Alan O'Connor and Kieran Treadwell at lock, and a back row of openside Clive Ross and Number Eight Nick Timoney alongside Henderson.
Blues raced into the lead inside two minutes, Evans finishing off a flowing move down the right wing from flanker Ellis Jenkins' sharp pass, and converting his own score.
Former Ulster favourite Nick Williams soon gifted Cooney three points after an illegal turnover, but Blues continued to dominate in open play and were good value for their second try on 12 minutes when Matthew Morgan's basketball-style pass to Blaine Scully outfoxed the Ulster rearguard and the winger sped over from 10 metres.
Ulster began to move well in midfield but were let down by careless passing on more than one occasion, both Piutau and Treadwell culpable as two promising attacks evaporated into thin air.
Worse still came on 28 minutes as Herbst found himself banished to the sinbin for a high arm on Evans as he attempted to clear out the ruck, but Ulster did well to hold off the Blues during the entirety of their numerical disadvantage - weathering the storm when Tomos Williams' touchdown on 36 minutes was ruled out for a forward pass.
There was still time in the half for Cooney and Evans to trade penalties, sending Ulster off at the break 11 points adrift.
Half-Time Score Cardiff Blues 17 Ulster 6
Ulster came out for the second period with the bit firmly between their teeth, gaining good ground through three successive penalties, the third of which Cooney elected to aim for the posts, reducing the gap to eight.
Now enjoying much better possession and territory, the visitors battered the Cardiff '22' for a good five minutes, eventually forcing another penalty in front of the posts which Cooney dispatched without fuss on 52 minutes.
A single try from parity now, Ulster toiled to resist the inevitable Blues backlash, but were undone once again by Evans, whose quick hands picked out replacement hooker Kristian Dacey to romp over from five metres just before the hour.
An off-target Cooney penalty moments later left Ulster chasing 10 points in the final quarter - soon bumped up to 13 after an Evans penalty - but the Blues, with the prospect of a bonus point now in their minds, slowed the game down and hemmed play deep in the Ulster half until a 70th-minute penalty allowed Evans to put the result beyond doubt.
Fine carrying from Timoney almost got replacement lock Matthew Dalton over for his first senior try three minutes later, only for the youngster to lose control of the ball before he could properly ground it.
The visitors' persistence finally paid off however, replacement scrum-half Shanahan nipping in at the corner from Gilroy's pass with a minute to go.
But there was enough on the clock for the Blues to pound down the other end, replacement prop Dillon Lewis bundling over after a good four minutes of stout Ulster defence.
The bonus-point victory strengthens Cardiff's position in Conference A, still in fourth but now a mere five points behind the Toyota Cheetahs, their opponents in the next round. Ulster, meanwhile, face a difficult run-in with their remaining clashes against Edinburgh, Ospreys, Glasgow and Munster.
Full-Time Score Cardiff Blues 35 Ulster 17
Cardiff Blues (15 - 9) Matthew Morgan; Blaine Scully, Rey Lee-Lo, Willis Halaholo, Owen Lane; Jarrod Evans, Tomos Williams
(1 - 8) Gethin Jenkins (c), Matthew Rees, Scott Andrews, George Earle, Seb Davies, Josh Turnbull, Ellis Jenkins, Nick Williams
Replacements (16 - 23) Kristian Dacey, Rhys Gill, Dillon Lewis, Ben Murphy, Macauley Crook, Lloyd Williams, Steve Shingler, Garyn Smith
Ulster (15 - 9) Charles Piutau; Craig Gilroy, Luke Marshall, Stuart McCloskey, Jacob Stockdale; Johnny McPhillips, John Cooney
(1 - 8) Andrew Warwick, Rob Herring, Wiehahn Herbst, Alan O'Connor (c), Kieran Treadwell, Iain Henderson, Clive Ross, Nick Timoney
Replacements (16 - 23) John Andrew, Callum Black, Ross Kane, Matthew Dalton, Matthew Rea, David Shanahan, Peter Nelson, Louis Ludik
Get up to date
Sign up to our eZine to receive updates, ticket and merchandise offers and the very latest Ulster Rugby news!