Following a 62-25 defeat to Exeter Chiefs in their competition opener the Blues responded with plenty of venom on home soil.
Reinforced with the return of a number of experienced heads they were level with their Swansea-based rivals for much of the encounter after Scott Otten and Rhodri Davies exchanged tries.
However the sending off of Anton Peikrishvili, early in the second-half, proved a turning point as Brendon Leonard quickly crossed the whitewash and Tom O’Flaherty struck on the counterattack as the Blues battled.
Ospreys took advantage of the extra minute as they secured a bonus point through Dan Evans in the final minutes, before Tom O'Flaherty dotted down for his second of the night.
It took the visitors just over a minute to open the scoring at BT Sport Cardiff Arms Park after they were awarded an early penalty by referee Ben Whitehouse.
They instantly displayed their attacking intent and kicked to corner with Otten burrowing over from the back of a driving lineout.
Phil Jones converted from the touchline to open up a 7-0 lead which remained for 15 minutes as both sides put the ball through hands but to little reward.
It was the Blues that broke the deadlock following some fine attacking phases. James Beal laid the foundations after Dan Fish and Garyn Smith combined and from the next phases scrum-half Jones sniped from the breakdown.
Fly-half Ben Jones, a pupil at Coleg y Cymoedd, knocked over the conversion to draw level and the Blues remained in the ascendant.
However, they were unable to turn their pressure into points as the scores remained 7-7 at the break with Phil Jones missing a last minute penalty.
Wales’ Capital Region made a flying start to the second-half with a sumptuous Dan Fish grubber down the left touchline breaking the Ospreys defence.
Owen Lane won the footrace but was unable to scoop the bobbling ball from his bootlaces at full pelt.
Cardiff Blues however were dealt a major blow on 46 minutes when Anton Peikrishvili was sent off following an altercation on the floor.
The Ospreys almost instantly replied as they kicked to the corner and set up a driving lineout with Brendon Leonard darting over.
Jones bisected the posts and after weathering a storm the Blues battled back. They were hammering away at the Ospreys’ defensive line but the ball was lost and the visitors struck on the counter-attack with Tom O’Flaherty racing clear.
In the dying minutes, a long pass across the Ospreys back line took advantage of the extra man, with Dan Evans given the easy task of toucing down to seal the bonus point, before another long range run from Tom O’Flaherty saw him dot down for his second of the night.