Leinster held off Cardiff Blues to strengthen their lead in the Pro12.
Sean O'Brien and Rob Kearney scored early tries for the visitors, both converted by fly-half Jonny Sexton who also kicked a brace of penalties.
Two Leigh Halfpenny penalties, a Dan Parks drop-goal and a close-range try from Gethin Jenkins brought the Blues to within a point.
Halfpenny kicked the conversion but crucially missed two penalties and Fergus McFadden booted Leinster clear.
Glasgow's loss at the Scarlets and defeat for the Ospreys at Newport Gwent Dragons on Friday means that Leinster now hold a handy nine-point lead at the top of the table, and are in good form ahead of next weekend's Heineken Cup trip to Glasgow.
The Blues, who had Gavin Henson withdraw before kick-off with a calf injury, are seventh in the Pro12 but top their Heineken Cup pool and now face what could be a make or break trip to London Irish.
The home side made a disastrous start as they conceded two early tries.
Leinster ran a free-kick, skipper Jamie Heaslip burst past a static defence and back row colleague O'Brien was at his shoulder to score.
Minutes later a move from the training ground saw full-back Kearney take an inside pass and knife through to touch down under the posts.
Sexton converted both to leave Leinster 14-0 ahead and seemingly in total control.
But the Blues, with fly-half Parks abandoning his usual kicking game to spread the ball wide, hit back with two penalties from Halfpenny before Parks, reverting to his usual script, dropped a goal.
Halfpenny was just short with an ambitious attempt from wide on the halfway line, but Sexton made no mistake with a much easier effort to end the first half with the visitors holding a 17-9 lead.
The Blues shot themselves in the foot on the restart, first by allowing Sexton's kick-off to bounce into touch inside their 22 and then having the line-out stolen by the alert O'Brien, but stout tackling meant Leinster had to settle for another Sexton penalty.
A further massive kick from Halfpenny took the Welsh region into double figures and the lively full-back then forced Leinster wing Dave Kearney to concede a five-metre scrum.
The Irish pushed too soon, yielding a free-kick, from which prop Jenkins forced his way over for a try eventually confirmed by the TV official. Halfpenny converted to reduce the deficit to just one point at 20-19.
A 60-metre kick by Halfpenny fell beneath the crossbar, but the Blues were causing all sorts of problems for the European champions, who had lost key men Gordon D'Arcy and Sexton to injury.
But they missed a chance to take the lead when Halfpenny fluffed a straightforward penalty and Leinster nerves were settled when McFadden slotted over a similar kick to confirm their victory.
Blues: Leigh Halfpenny; Richard Mustoe, Casey Laulala, Gavin Evans, Tom James; Dan Parks, Lloyd Williams; Gethin Jenkins, Marc Breeze, Scott Andrews, Macauley Cook, Michael Paterson, Maama Molitika, Sam Warburton (capt), Xavier Rush.
Replacements: Rhys Williams for Breeze (42), John Yapp, Sam Hobbs for Andrews (74), Matthew Screech, Josh Navidi for Molitika (48), Richie Rees for L. Williams (48), Ceri Sweeney, Harry Robinson for Mustoe (73).
Leinster: Rob Kearney; Dave Kearney, Fergus McFadden, Gordon D'Arcy, Andrew Conway; Jonathan Sexton, Eoin Reddan; Cian Healy, Sean Cronin, Mike Ross, Mark Flanagan, Devin Toner; Kevin McLaughlin, Sean O'Brien, Jamie Heaslip (capt).
Replacements: Aaron Dundon, Heinke van der Merwe for Healy (70), Jamie Hagan, Leo Auva'a for Flanagan (74), Jordi Murphy for McLaughlin (41), Isaac Boss, Isa Nacewa for D'Arcy (38), Fionn Carr for J. Sexton (58).
Referee: Marius Mitrea (Italy)
Assistant Referees: Neil Hennessy, Phil Fear (both WRU)
Citing Commissioner: Gwyn Bowden (WRU)
TMO: Neil Ballard (WRU)