Anthony Foley’s men built an 11-6 interval lead in Limerick with CJ Stander crossing for a 16th-minute try.
Andrew Conway came back to haunt his former team with a well-taken try in the 44th minute and during Darragh Fanning’s sin-bin period, Munster replacement Dave O’Callaghan collected try number three before Ian Keatley capped off his 13-point kicking haul.
Stand-in captain Shane Jennings responded with Leinster’s lone try, but they could not avoid their first league defeat since Munster visited them in early October.
The Irish Rugby Football Union player welfare programme may have robbed this festive fixture of some of its headline acts - including the likes of Peter O’Mahony, Paul O’Connell, Rob Kearney and Jamie Heaslip - but it was, nonetheless, a full-blooded encounter. Keatley and Ian Madigan swapped early penalties, Munster forcing a maul infringement initially and then their loosehead John Ryan was pinged for not rolling away quickly enough.
Faced with bunched midfields, both kickers cleverly exploited the space in behind before the Munster pack got on the front foot with some muscular carries. Leinster had to replace a groggy Dominic Ryan and as they adjusted, the hosts struck for the game’s opening try. It was 11-6 at the interval and Munster built on that.