They ended up fourth in Conference A – in the process sealing a return to the European Champions Cup.
For four seasons on the spin the Welsh capital region had been in the second tier Challenge Cup but now they are back in the big time.
And they capped up an impressive campaign by winning the Challenge Cup in Bilbao with a dramatic victory over Gloucester.
The big news for next season however, as they look to build on a breakthrough year, comes off the field with the appointment of John Mulvihill as their new head coach.
The playing stocks have not altered dramatically – with Alex Cuthbert and Damien Welch departing and Taufa’ao Filise retiring, but here are three players to watch out for next season.
An Ospreys fans favourite, the Moldovan prop makes the short switch to the Blues for next season and will be a vital boost their front-row options.
The 29-year-old had appeared in over 100 games for the Ospreys in his five seasons there but the Blues and Mulvihill have pulled off a real coup in signing him.
With club legend Filise finally hanging up his boots, the Blues needed a tighthead to make a difference and Arhip offers solidity in the set-piece and power in the loose.
With a number of big Top 14 clubs thought to be circling the Moldovan, the Blues have swept in and acquired the world-class front rower ahead of the new season.
— PRO14 RUGBY (@PRO14Official) July 21, 2018
The other Blues signing of the off-season is Jason Harries from Edinburgh.
The Welshman will add depth to a competitive back three – despite the departure of British & Irish Lion Cuthbert.
But Harries will have his work cut out for him if he is to take minutes off the new Welsh sensation Owen Lane.
Lane burst onto the scene halfway through last season and the powerful winger, 20, also inked a new deal at the Arms Park.
Next season is sure to be a big one for Lane and the youngster will be itching to prove his worth from the outset and get onto Warren Gatland’s radar as well.
— PRO14 RUGBY (@PRO14Official) July 18, 2018
Gareth Anscombe has been making a real play for the No.10 jersey with Wales.
But for his own region, he had to settle for the full-back position in the second half of the last campaign – such was Jarrod Evans’ form at fly-half.
Still only 21, the former Wales Under-20s No.10 has pulled the strings in superb fashion for the Blues as they finished the season in style – securing top flight European rugby next season.
And Evans will be keen to build on that strong finish next year and see if he can catapult himself into the international arena as well.