However they finished the stronger side, minced the Leinster scrum to earn the penalty try and ended the game attacking the Leinster line in added time, their last gasp assault spear-headed by treplaceement Tomas O'Leary whose off-load was knocked on for Leinster to clear to touch.
Johnnny Sexton kicked 21 of Leinster points with Rob Kearney landing a drop goal while Ronan O'Gara kicked four penalties and a conversion.
Munster lost Keith Earls right at the start when he was injured after taking Sexton's kick off, replaced by Danny Barnes.
O'Gara kicked Munster into the lead with a 4th minute penalty but two Sexton strikes in the space of five minutes left the home narrowly in front before O'Gara tied it up again with a 19th minute penalty.
A penalty against Munster for coming in from the side let Sexton edge the home side in front but moments later the same offence from Leinster went unpunished.
A penalty for offside gave Sexton a tap over for a 12-6 lead but O'Gara was again on the mark minutes later.
Shortly before the break a forward pass decision allowed Leinster retain good field position and when the penalty was conceded Sexton restored his side's six point advantage going into the break.
Munster: J Murphy; D Howlett, W Chambers, L Mafi, K Earls; R O'Gara, C Murray; W du Preez, D Varley, BJ Botha; D O'Callaghan, P O'Connell capt; D Ryan, N Ronan, D Leamy. Replacements. D Fogarty, M Horan, J Hayes, P O'Mahony, J Coughlan, T O'Leary, I Keatley, D Barnes.
Leinster: R Kearney; I Nacewa, F McFadden, G D'Arcy, L Fitzgerald; J Sexton, I Boss; C Healy, R Strauss, M Ross, L Cullen capt, D Toner, S O'Brien, S Jennings, J Heaslip. Replacements: S Cronin, H van der Merwe, J Hagan, K McLoughlin, R Ruddock, E Redden, I Madigan, E O'Malley.
Referee: P Gauzere (FFR)