|Cardiff Blues (13) 13|
|Try: Anscombe Con: Anscombe Pen: Anscombe|
|Leinster (3) 16|
|Try: Ruddock Con: Sexton Pens: Sexton (2)|
Cardiff Blues suffered their first defeat of the season as Leinster turned around a 10-point deficit to win at the Arms Park.
A virtuoso display by fly-half Gareth Anscombe - including a wonderful solo try - had Blues in charge.
But Leinster hit back with a try by Rhys Ruddock, and Johnny Sexton's 70th-minute penalty edged them ahead.
With Josh Navidi in the sin-bin, Blues spurned a kickable late penalty chance to go for a try, but were held out.
The victory lifts Leinster into third place in the Pro12 table, a place ahead of the Blues on points difference and a point behind their next opponents, Munster.
The loss for Danny Wilson's team leaves Ulster as the only side with a 100% record in the league.
Wales captain Sam Warburton suffered a blow to the face early in the game and was replaced by Navidi.
Blues were behind early on to Sexton's penalty, but the rest of the first half belonged to Anscombe.
He cancelled out Sexton's effort and lifted the roof off the Arms Park as he scorched over from 40 metres, converting his own try.
His long-range penalty then gave Blues a 10-point cushion at the interval.
Leinster upped their game early in the second half, with Sexton kicking a second penalty and Ruddock driving over from close range with Blues defenders claiming he had made a double movement.
The scores were tied with 10 minutes remaining when Navidi was penalised for offside and promptly shown a harsh-looking yellow card by referee Dudley Phillips.
Sexton made no mistake from in front of the posts.
In a nail-biting finale, Anscombe opted to go for touch rather than take a kick at goal, and when the Blues spilled the ball, man-of-the-match Sexton hoofed it off the park to secure the points.
Cardiff Blues: Matthew Morgan; Blaine Scully, Cory Allen, Rey Lee-Lo, Tom James; Gareth Anscombe, Lloyd Williams; Gethin Jenkins (capt), Kristian Dacey, Taufa'ao Filise, George Earle, Josh Turnbull, Sam Warburton, Ellis Jenkins, Nick Williams
Replacements: Matthew Rees, Rhys Gill, Scott Andrews, Macauley Cook, Josh Navidi, Tomos Williams, Steve Shingler, Dan Fish
Leinster: Zane Kirchner; Fergus McFadden, Rory O'Loughlin, Noel Reid, Dave Kearney; Johnny Sexton, Jamison Gibson-Park; Jack McGrath, James Tracy, Mike Ross, Mick Kearney, Ian Nagle, Dan Leavy, Josh van der Flier, Rhys Ruddock
Replacements: Sean Cronin, Peter Dooley, Michael Bent, Devin Toner, Jamie Heaslip, Nick McCarthy, Joey Carbery, Barry Daly
Referee: Dudley Phillips (IRFU)
Assistant Referees: Frank Murphy (IRFU), Ian Davies (WRU)
Citing Commissioner: Gwyn Bowden (WRU)
TMO: Neil Paterson (SRU)