Blues made a bright start with Leigh Halfpenny kicking them into an early lead before Leinster hit back with a well-crafted try from hooker Sean Cronin.
Fly half Ian Madigan nudged the Irish side, inspired by the ever-green Brian O’Driscoll, further ahead.
But Blues really fronted up and produced some neat and inventive rugby in the opening 40 minutes as they deservedly trailed just 13-6 at the interval.
A man down after a yellow card to Filo Paulo, Blues conceded a penalty try at the start of the second half
A superb solo try from Alex Cuthbert saw Blues fight-back and Harry Robinson than had an effort ruled out for a forward pass as the visitors really mounted a spirited challenge.
Leinster, though, wrapped up the win with a driving lineout score 13 minutes from time and a late try from Madigan secured the bonus point. The alert Cory Allen intercepted a late try for Blues.
Fit-again flanker Sam Warburton was one of five changes for Blues while Leinster rang the changes with Brian O'Driscoll and Jamie Heaslip both making their first appearances of the season.
The duo were joined by fellow Lions Cian Healy and Rob Kearney in a side that showed 12 changes in total from last weekend's defeat by Glasgow.
An early penalty gave Halfpenny the chance to open the scoring but his effort pulled up just short and right of the uprights.
Centre Owen Williams, who has impressed in the opening weeks of the season, produced another magical run to ease past two men and take Blues deep into Leinster territory.
The TMO came into play early on and Blues were the beneficiaries as play was taken back and Halfpenny slotted the first penalty of the game after six minutes.
Blues were playing some smart rugby in the opening minutes as Cuthbert found a gap from deep and raced past men before being halted by a shuddering tackle from Dave Kearney.
The forwards were really eager to carry ball as Josh Navidi broke a tackle before back row partner Warburton was strong to carry forward in contact.
Irish ace Rob Kearney produced a superb long clearing kick to force Blues back, but back came another wave of visiting attack with Rhys Patchell produced a sublime offload to Owen Williams but he could not quite find the supporting Harry Robinson who was crowded out.
Fergus McFadden sparked Leinster into life for the first time with a neat grubber kick and it was the hosts that broke through as Brian O’Driscoll’s pass was perfectly timed to Cronin on the angle to dot down.
O’Driscoll was in the thick of the action as this time he collected Rob Kearney’s pass and broke down the middle before flicking back into the hands of the marauding full back. Rhys Ruddock then galloped past a tackle but as the home crowd roared the ball was spilled.
Scrum half Isaac Boss then spotted a hole and darted for the line, but lost control as the tackles came in from Warburton and Taufa’ao Filise before Patchell was hurried into a clearance as Leinster turned the screw at scrum time.
A penalty for not rolling away gave Madigan another chance to extend the lead and with just over quarter of the game gone he confidently drilled over his kick.
Three later Patchell intercepted a pass, just moments after a sensational piece of play from O’Driscoll as he passed out of the back of his hand, but he was quickly swarmed upon by home players and another penalty saw the same result and a 13-3 lead.
A long hack ahead by Matthew Rees, after Leinster spilled ball at the base, saw wing Robinson denied by jet-heeled opposite number McFadden as he touched back.
The resulting five-metre scrum to Blues gave them a big attacking opportunity, and when Halfpenny made a dash the home side were penalised for killing the ball. The full back brushed himself down and made no mistake to cut the lead on the half hour.
Warburton was back doing what he does best with a brilliant turnover after the home back line again threatened to click into gear with some devastatingly quick handling down the line.
Leinster again looked to strike from deep with O’Driscoll the architect once more as he fed Rob Kearney but he was dragged into touch by Patchell, who had to show all his pace to keep up.
The home side started the second half determined to put the game to bed as Jamie Heaslip punched a hole in the defence before the forwards rattled up close as under pressure Blues held firm on the line.
Lock Filo Paulo was yellow carded as Blues tried to stem the home tide and, with the numerical advantage, the home side were awarded a penalty try by the referee as a scrum collapsed as it rumbled to the line.
Blues fought their way back into the game and a scintillating solo try from Lions wing Cuthbert saw him show his electric pace down the wing before cutting inside and bursting over.
McFadden thought he had hit back immediately as he looked to smash his way over but he was held up, after lengthy consultation with the TMO by the officials.
Blues again almost exploded into life as Owen Williams again made a line break and offloaded to Patchell who in turn found Cuthbert. The winger did not quite have the speed to breakaway and his pass sent Robinson over but it was ruled out for a forward pass.
A charge down on a Lloyd Williams kick saw Leinster win a penalty and kick for the corner. The brave decision paid off as the home pack drove Dominic Ryan over to secure the win.
Madigan added the conversion and then applied the late gloss as he darted over to secure the home side the bonus point win.
Blues had the final word as replacement Cory Allen swooped to pick off a pass and run over unopposed.
06m Halfpenny p 0-3
14m Cronin t Madigan c 7-3
22m Madigan p 10-3
25m Madigan p 13-3
30m Halfpenny p 13-6
49m Penalty t Madigan c 20-6
53m Cuthbert t Halfpenny c 20-13
67m Ryan t Madigan c 27-13
74m Madigan t Madigan c 34-13
78m Allen t Patchell c 34-20
Cardiff Blues: 15 Leigh Halfpenny, 14 Alex Cuthbert, 13 Owen Williams, 12 Dafydd Hewitt (Allen 70), 11 Harry Robinson, 10 Rhys Patchell, 9 Lloyd Williams (Jones 76); 1 Sam Hobbs (Davies 58), 2 Matthew Rees, 3 Taufa’ao Filise, 4 Lou Reed (Down 69, Dacey 72), 5 Filo Paulo, 6 Josh Navidi, 7 Sam Warburton, 8 Andries Pretorius (Copeland 69)
Replacements: 16 Kristian Dacey, 17 Thomas Davies, 18 Scott Andrews, 19 James Down, 20 Robin Copeland, 21 Lewis Jones, 22 Gareth Davies, 23 Cory Allen
Leinster Rugby:15 Rob Kearney, 14 Fergus McFadden, 13 Brian O'Driscoll (Macken 73), 12 Noel Reid, 11 Dave Kearney, 10 Ian Madigan (Gopperth 76), 9 Isaac Boss (Cooney 69); 1 Cian Healy (McGrath 69), 2 Sean Cronin (Dundon 70), 3 Martin Moore (Ross 64), 4 Devin Toner, 5 Quinn Roux, 6 Rhys Ruddock (Murphy 69), 7 Dominic Ryan, 8 Jamie Heaslip
Replacements:16 Aaron Dundon, 17 Jack McGrath, 18 Mike Ross, 19 Tom Denton, 20 Jordi Murphy, 21 John Cooney, 22 Jimmy Gopperth, 23 Brendan Macken