Cardiff Rugby battled to claim a losing bonus-point in attritional BKT United Rugby Championship encounter at Affidea Stadium on Saturday night.
Ulster dominated the first-half in Belfast and bludgeoned their way into a 14-0 lead thanks to tries from props Scotty Wilson and Angus Bell.
But the Blue & Blacks battled bravely and dragged their way back into the encounter with a try from Johan Mulder.
Charlie Irive restored Ulster’s 14-point advantage but Cardiff quickly replied with Stef Emanuel finishing a fine try, which Sheedy converted.
That brought Cardiff within seven and they clung on under immense pressure in the closing stages to leave Northern Ireland with what could be a crucial extra point in the race for the play-offs.
The Blue & Blacks, without some 18 players due to international selection and injury, made nine changes to the team that battled past Benetton a week ago.
They were without all eight of their Wales squad members but benefitted from the availability of Wales Under-20s co-captain Steffan Emanuel and star wing Tom Bowen.
The hosts dominated the opening 10 minutes at Affidea Stadium, pinning Cardiff deep in their own 22 with an effective kicking game.
The pressure eventually took its toll as Scotty Wilson crashed over from close range following a break down the left, which saw Werner Kok combine with Matt Dalton and Dave McCann. Jack Murphy added the extras to give his side a 7-0 lead after 12 minutes.
Ulster continued to control affairs, and they claimed a second try just seven minutes later. Again it was scored by a prop but while Wilson’s effort was all about close-range power, Angus Bell’s was one which any wing would savour.
The Australia international burst through a gap at the back of the breakdown before sidestepping. Murphy was again on target as Ulster took a 14-0 into the break.
While Ulster controlled the first-half, there was much more for Cardiff to be encouraged by in the second. They grew into the encounter, punching above their weight against a gargantuan Ulster side.
They threatened on the edges with Callum Sheedy and Stef Emanuel putting clever kicks behind. Ulster were up to task but Cardiff were well in the encounter and they struck on 54 minutes.
Following some big carries from the pack, Mulder was lightning quick after Javan Sebastian went close, scooping the ball at full pace to snipe over. Sheedy knocked over the simple conversion to make it 14-7.
Cardiff were dealt a blow on 66 minutes when Ulster struck from their first real period of territory in the second half.
The Blue & Blacks should have relieved pressure but conceded a scrum against the head and failed to recover. Ulster went through two phases with quick recycles to allow Charlie Irvine to crash over.
Murphy converted to bring the scores to 21-7 but Cardiff were undeterred and hit-back within a minute.
The tireless Alun Lawrence took the ball to the line before possession was moved to Taine Basham and the explosive backrower burst through the Ulster midfield.
He tore into the Ulster half and passed to Emanuel who showed brilliant pace to evade Werner Kok and claim a fine try. Sheedy converted to bring the Blue & Blacks to within seven points.
Cardiff had further chances but just as they were pressing they were, perhaps harshly penalised, and Ulster cleared down field.
They piled on the pressure in the closing stages and hammered away at the Blue & Black wall, appearing to score with the last play, but Dave Shanahan was off his feed as he picked up and placed the ball on the whitewash.