In an evenly contested opening half Munster led 13-3 at half time.
Thomas Quinlan put them ahead with a penalty after two minutes and extended the advantage to six with his second effort on twenty minutes.
Leinster opened their account three minutes later with a penalty from Joey Carbery.
Pressure by the Munster pack resulted in Shane McAuliffe going in for a try and Quinlan converted to leave it 13-3 at half time.
A great break by Munster's Stephen McMahon saw the skipper being stopped short of the line, but the ball was recycled and from a ruck Frank Bradshaw Ryan crashed over the line for an 18-3 lead.
Substitute Dylan Horgan made it 21-3 with a penalty after fifty five minutes.
Ben Kilkenny scored Munster's third try and Horgan converted.
A late Leinster rally saw tries from Michael Courtney and Conor Oliver and Fergal Cleary converted one to leave the score 28-15.
Munster: Stephen Fitzgerald (Ard Scoil Rís); Shane McAuliffe (CBC), Stephen McMahon (Captain) (Rockwell College), JJ O'Neill (Crescent College Comp.), Brion Moriarity (Ard Scoil Rís); Tomas Quinlan (CBC), Jack Cullen (Munster Academy); Liam O'Connor (CBC), Sean McNulty (Rockwell College), Michael O'Donnell (Crescent College Comp.); Jonathon Keane (Crescent College Comp.), Frank Bradshaw Ryan (Ard Scoil Rís); Jack Boland (Glenstal Abbey School), Luke O'Leary (Sunday's Well), Ben Kilkenny (St. Munchin's College).
Replacements: Jack O'Halloran (Ard Scoil Rís), Denis O'Connell (Rockwell College), Brendan Quinlan (Rockwell College), Darragh Power (Waterpark), Cormac Blake (Crescent College Comp.), David O'Mahony (Rockwell College), Dylan Horgan (Highfield), Eoin O'Carroll (Tralee).
Leinster: Robert Vallejo (New Ross); Cian O'Donoghue (Clongowes Wood College), Cormac Brennan (C.C. Roscrea), Michael Courtney (CBC Monkstown), Cillian Burke (Clongowes Wood College); Fergal Cleary (Clongowes Wood College), Joey Carbery (Blackrock College); Jeremy Loughman (Blackrock College), Andy Roche (Terenure College), Hugh O'Donnell (Newbridge College); Jack Dwan (Blackrock College), Collie Joyce-Aherne (Wexford Wanderers); James Doyle (Belvedere College SJ), Patrick Thornton (Terenure College), Nick Timoney (Blackrock College) (C).
Replacements: Liam Walshe (Wicklow), Jonathan Phelan (Newbridge College), Eric O'Sullivan (Templeogue College), Alex Penny (St. Michael's College), Conor Oliver (Skerries), Andy Purcell (Mullingar), Tim Schmidt (Terenure College), Mark Sutton (Newbridge College).
Munster's Captain Steve McMahon on the charge
Munster's Ben Kilkenny tries to break through a Patrick Thornton tackle