The Blues’ second successive bonus point win piled pressure on Pool Six rivals Gloucester, whose quarter-final hopes suffered a serious setback.
Blues’ record Heineken Cup crowd of just over 27,000 witnessed a free-flowing encounter underpinned by faultless goalkicking from Ben Blair and Olly Barkley.
Teenage wing Leigh Halfpenny scored two incisive tries for the home side, while former Wales captain Gareth Thomas and fly-half Nicky Robinson also crossed to keep Gloucester at a safe distance.
Blair’s kicking — 17 points from seven kicks — ultimately made the difference, although Gloucester played their part, with wing Iain Balshaw claiming a try double and full-back Olly Morgan touching down.
Barkley booted three conversions and a penalty, but Gloucester lost both Morgan and fly-half Ryan Lamb to injuries on a day they will want to forget.
Gloucester arrived in the Welsh capital looking to take a grip on their group after beating Biarritz last time out, while the Blues were fresh from a 50-point victory over Calvisano.
Blues head coach David Young said: “We weathered a few storms out there. There were big parts of the game when it could have gone either way.
“We have four pool fixtures left, and we’ve got to win three of those — that has to be our focus.”
Young also hailed a superb man-of-the-match display from number eight Andrew Powell, whose performance might thrust him into autumn Test contention.
It was a final chance for Blues players to impress Wales coach Warren Gatland before he names his autumn Test squad on Tuesday.
Meanwhile Gloucester boss Dean Ryan accepts his team face “a big task” to reach the quarter-finals.
Gloucester, Heineken Cup quarter-finalists last season, are now unlikely to repeat that feat unless they win their four remaining Pool Six games, which includes a trip to Biarritz in January.
Ryan said: “It will be a big task now. This has put us on the back foot, and we will have to do something special at Kingsholm.
“I am disappointed we didn’t win the game. I thought we had a lot of control, and I thought we looked very threatening.”
Cardiff Blues scorers: Tries: Halfpenny 2, G. Thomas, N. Robinson. Cons: Blair 4. Pens: Blair 3.
CARDIFF BLUES: Blair, Halfpenny, J. Robinson, Shanklin, G. Thomas, N. Robinson, Spice, Jenkins, T. Thomas, G. Powell, Jones, Tito, Molitika, M. Williams, A. Powell, J. Roberts.
Replacements: J. Roberts for Shanklin (53), Rees for Spice (67), Morgan for Jenkins (76), G. Williams for T. Thomas (57), Filise for G. Powell (53), Sowden-Taylor for M. Williams (74), Sweeney for J. Roberts (78).
Gloucester scorers: Tries: Morgan, Balshaw 2. Cons: Barkley 3. Pens: Barkley.
GLOUCESTER: Morgan, Balshaw, Tindall, Barkley, Simpson-Daniel, Lamb, Cooper, Dickinson, Azam, Nieto, Bortolami, Brown, Buxton, Strokosch, Narraway, Hazell.
Replacements: Walker for Morgan (44), Vainikolo for Lamb (36), R. Lawson for Cooper (72), Hazell for Buxton (53), Eustace for Narraway (78), S. Lawson for Hazell (72).
Referee: Alain Rolland (Ireland).