Gareth Thomas, with a try, and Neil Jenkins, with 15 points, signed off their Brewery Field careers in style as the Celtic Warriors left the Blues' European hopes in tatters.
Warriors 10 (30):
Tries: Horsman, Parker, Thomas.
Cons: Jenkins 3.
Pens: Jenkins 3.
Blues (16) 26:
Tries: Shanklin, Morgan, R Williams.
Pens: Harris 3.
Thomas leaves for Toulouse at the end of the season, while world record Test points scorer Jenkins will retire.
Tries from Tom Shanklin, Craig Morgan and Rhys Williams gave Blues hope in the race to make the Heineken Cup.
But Warriors matched the visitors' try count and Jenkins' boot did the rest.
The Warriors had needed just a point to ensure they play in the Heineken Cup next season, but the Blues are now favourites to enter the second tier Parker Pen Cup.
The side from Cardiff trail the Ospreys by three points and must hope the Neath-Swansea side lose to the Scarlets in their penultimate match of the season on Sunday.
The visitors started the match in stunning fashion, taking less than than three minutes to cross the Warriors' try line.
Jamie Robinson sent a perfect chip in behind defending wing Gareth Wyatt, who was beaten to the bouncing ball by Shanklin on the charge.
Iestyn Harris missed the conversion, but made amends with a penalty soon after to give the Blues a handy 8-0 lead.
That advantage should have been greater but Nick Robinson got his weight of pass all wrong with a man overlap beckoning, sending the ball into touch instead.
Then came another set-back for the Blues when Martyn Williams earned 10 minutes in the sin-bin for impeding Wyatt when taking a quick tap-penalty.
With a man advantage, prop Chris Horsman barrelled his way over from a driving maul for the Warriors' opening score on the quarter-hour mark, converted by Jenkins.
Referee Alain Rolland evened up the playing numbers when Warriors full-back Emyr Lewis was yellow-carded for killing the ball illegally.
With extra space to work with the Blues backs let rip, Harris drawing Sonny Parker before popping the perfect pass to Jamie Robinson.
Lock Jim Brownrigg provided excellent support and it was left to wing Morgan to race over for an unconverted try to make it 13-7 to the men from Cardiff.
Harris and Jenkins exchanged penalties as the half ran out, leaving the Blues leading 16-10 at the break.
The Warriors kept it strong and simple from the restart, the pack buckling down and Jenkins kicking for territory to put the Blues under pressure.
The tactic paid dividends as the Blues began to make more errors in dangerous areas, allowing Jenkins to add two more penalties to level the scores.
The tide appeared to have turned and the Warriors took the lead for the first time when Parker shoved off Jamie Robinson to go in under the posts for a converted try and a 23-16 lead after 58 minutes.
The Blues remained dangerous, however, and the visitors went the length of the pitch from a turnover to send Rhys Williams over the try line, Harris' conversion levelling the scores again.
Then with 20 minutes remaining came the score the home fans wanted, Thomas scoring his last try at the Brewery Field before he departs for France and Toulouse at the end of the season.
But the decision looked generous from the replays as Thomas appeared to have made a double movement, but to the Blues' disbelief the try stood.
Cory Harris became the second Warriors player sin-binned for hauling Dean Dewdney back off the ball, a harsher referee might have awarded a penalty try but Harris at least narrowed the gap to 30-26 from the penalty kick.
It was enough to earn the visitors a bonus point in defeat, but the Blues' hopes of qualifying for next season's Heineken Cup now hang by a thread.
Warriors: E Lewis; D James, S Parker, G Thomas, G Wyatt; N Jenkins, G Cooper; G Jenkins, M Davies, C Horsman, B Cockbain, R Sidoli, M Molitika, C Harris, R Bryan.
Replacements: M Jones, M Rees, D Jones, R Parks, C Sweeney, P John, J Bryant.
Blues: R Williams; T Shanklin, J Robinson, I Harris, C Morgan; N Robinson, D Dewdney; J Yapp, R Thomas, B Evans, H Senekal, J Brownrigg, D Baugh, M Williams (capt), N Thomas.
Replacements: D Crompton, A Lewis, C Quinnell, R Sowden-Taylor, A Moore, N MacLeod, M Allen.
Referee: Alain Rolland (Ireland).