In blustery and testing conditions, it was defences that were dominant for much of the match in Swansea.
Young playmaker Jarrod Evans, on his first PRO12 start, gave Cardiff Blues an early lead that they held onto until the break.
A further long range effort from Evans extended the lead before the home side took the lead 20 minutes from time when Welsh lock and home skipper Alun Wyn Jones crashed over from close range.
Replacement Sam Davies nudged Ospreys further ahead in the downpour and despite a late fight-back it was the hosts that claimed the points on offer while Blues were left to reflect on a more encouraging display.
Head Coach Danny Wilson made four changes to his starting line-up with Sam Warburton and Lou Reed called into the pack while Dan Fish and fly half Evans, for his full PRO12 debut, joined the backs.
And a lively start from the visitors saw Reed and Dacey twice offer themselves as runners before Lloyd Williams kicked in behind and forced Dan Biggar to race back and mop up danger in horrible handling conditions.
Rey Lee-Lo and Sam Warburton combined to win a penalty on the floor and fly half Evans confidently slotted the kick into driving rain for the lead after seven minutes.
Ospreys looked to respond with Dan Evans kicking in behind and after a ricochet off Scully and Lee-Lo it was Fish who hacked the ball out. More pressure followed but after 19 phases the visitors forced a knock-on after some resolute defence.
Manoa Vosawai peeled away after the first scrum of the game held firm while Jarrod Evans showed his confidence as he took a grubber kick and stepped inside Eli Walker.
All-action prop Gethin Jenkins looked hungry for work as he hurtled into a tackle on Alun Wyn Jones but a spilled pass in midfield saw Ospreys look to attack wide from Biggar’s chip into space for Tom Grabham.
Ospreys were controlling territory and possession, but in wretched conditions the visitors were holding firm to maintain a lead at the midpoint of the first half.
A scrum penalty saw Biggar kick to the corner to set up a lineout drive, but Blues again held strong and then looked to counter from lost ball with Tom James cutting inside from Lee-Lo’s quick flat pass.
Spilled ball from Walker gave Blues an attacking platform that Scully looked to use before the forwards shunted up with Vosawai and James Down prominent.
Flanker Turnbull twice unloaded big tackles on rampaging men, but a charged down box kick by home Number Eight Dan Baker sparked a manic period as Ospreys looked to exploit a splintered defence with Dan Evans an elusive runner.
Cardiff Blues were dealt a blow with Warburton forced off after rolling his ankle while Tom James was also taken from the field after a knock to the head and never returned.
Wilson’s men looked to come alive before the break with Macauley Cook hacking ahead but Brendon Leonard this time picked up and fed Biggar to clear his lines.
Evans missed with a penalty kick from out wide, after Lee-Lo and Isaacs combined down the touchline with some neat handling despite the cold and blustery conditions, as Blues took a battling 3-0 lead into the break.
A penalty at the start of the second half for Sam Davies, on for Biggar at the interval, dropped wide left to give Blues a reprieve after a needless lineout penalty for dragging down.
Lee-Lo twice hauled men back as he raced out of the defensive line with disruptive consequences while the energetic Cook latched onto Fish’s high hanging kick to make 20 metres and force territory.
More and more contested high balls were going up into the murky skies above the Liberty wirth Scully flying high to take one under huge pressure from wing Walker.
A scrum penalty saw Evans slot a long range penalty while Justin Tipuric took a quick tap and go but more solid defence saw Fish win a penalty for holding on.
The rain was now hurling down forcing both teams into errors, but the home side were slowly growing in confidence and the forwards took the game by the scruff of the neck as they bulldozed up close before home skipper Wyn Jones crashed over. Davies converted for the lead.
Blues looked to hit back but this time it was Ospreys who were holding firm as Evans looked to orchestrate a way back into the game with half back partner Williams. But a penalty for not rolling away saw Davies nudge the home side further ahead.
Lost ball in contact in the 22 set Lee-Lo away and Vosawai hurtled into a defensive wall before another penalty let Ospreys off the hook after they had caused their own problems.
Davies missed a long range penalty wide right, but was allowed to make amends within 60 seconds after another shot at goal was conceded with after obstruction.
And despite a late charge and period of possession deep into stoppage time, it was the Ospreys who took the win while Cardiff Blues will look to build on the bonus point as they face Connacht at home next Friday.
Timeline:
07m J Evans p 0-3
52m J Evans p 0-6
59m Wyn Jones t S Davies c 7-6
69m Davies p 10-6
78m Davies p 13-6
Cardiff Blues: 15 Dan Fish, 14 Blaine Scully, 13 Rey Lee-Lo, 12 Gavin Evans, 11 Tom James (Isaacs 32), 10 Jarrod Evans (G Davies 76), 9 Lloyd Williams (Knoyle 71); 1 Gethin Jenkins (Hobbs 72), 2 Kristian Dacey (E Lewis 40), 3 Taufa’ao Filise (Mitchell 62), 4 Lou Reed (Hoeata 59), 5 James Down, 6 Josh Turnbull, 7 Sam Warburton (Cook 32), 8 Manoa Vosawai
Replacements: 16 Ethan Lewis, 17 Sam Hobbs, 18 Craig Mitchell, 19 Jarrod Hoeata, 20 Macauley Cook, 21 Tavis Knoyle, 22 Gareth Davies, 23 Tom Isaacs