A single try from Leinster hooker Sean Cronin made the difference this evening at the RDS as Ulster came off second best in a tight clash dominated by highly-committed defending from both sides.
Paddy Jackson's early penalty ended up Ulster's solitary score in a display which represented a marked improvement from last week's European defeat to Saracens, but which saw the province remain fifth in the standings despite the collection of a losing bonus point.
Ruan Pienaar ran out at the RDS for his 100th Ulster cap - and first start in the Guinness Pro12 this season - alongside four other new faces in the first XV, with Peter Nelson coming in at full-back, and Kyle McCall, Robbie Diack and Sean Reidy all slotting into the pack.
Andrew Trimble and Craig Gilroy occupied the wings, with Darren Cave and Stuart McCloskey continuing in the centre, and Jackson partnering Pienaar in the half-backs. Prop McCall lined up in the front row with captain Rory Best and Wiehahn Herbst, while Iain Henderson moved into the second row alongside Dan Tuohy, and Nick Williams joined Diack and Reidy at the base of the scrum.
With both teams eager to start well after indifferent displays and results in the European Rugby Champions Cup, an early offside from Herbst gifted Johnny Sexton a sixth-minute penalty, before the same infringement from Mike McCarthy gave Jackson the chance to equalise three minutes later - but his kick veered inexplicably wide.
The Ulster out-half made no such mistake on 13 minutes with a composed strike from a marginally more challenging angle, and his side continued to hold their own, with a pinpoint kick to the corner again from Jackson putting Leinster under the severe pressure of a five-metre lineout on 20 minutes.
The hosts cleared their lines well and, from a similar set-piece in attack five minutes later, only Diack's bulk prevented Josh van der Flier from touching down off the back of a rolling maul, holding the player up over the whitewash to force the five-metre scrum. Ulster then repelled the Leinster push manfully, forcing play out wide where Isa Nacewa's hurried pass eluded Zane Kirchner and dropped into touch.
Sexton opted to kick two late first-half penalties to touch, losing possession in the first lineout to Diack. However the second ran like clockwork, with Cronin picking up off the back of the lineout drive to ground the try on 38 minutes, although Sexton's conversion sailed wide.
Half-Time Score Leinster 8 Ulster 3
Leinster made a lively start to the second half, all three of their back-rowers causing havoc with ball in hand until Rhys Ruddock shrugged off Tuohy's tackle to break the line and find Sexton, whose final pass to Ben Te'o was just too firm for the centre to hold onto as a certain try beckoned.
The Leinstermen came again on 47 minutes, this time Best the hero as van der Flier was once again held up over the line, and fantastic defence from Ulster for the next five minutes eventually saw them wrestle back possession. As the visitors pushed upfield, strong interplay between their wingers got them deep into the Leinster '22', but a sluggish approach from the forwards five metres from home, with Diack holding on too long in the tackle, conceded possession with no points scored.
Into the final quarter, Ulster enjoyed some good possession between half-way and the opposing '22' until the ever-impressive van der Flier disrupted Henderson and replacement Roger Wilson sufficiently to force the knock-on.
Possession of the ball surrendered, Ulster got bogged down in their own '22' five points adrift with three minutes remaining, only retrieving it with thirty seconds to go and, although they pressed for a further three minutes deep into stoppage time, a dropped ball from Chris Henry saw Leinster clear and Les Kiss' side depart Dublin with the scant consolation of a losing bonus point.
Full-Time Score Leinster 8 Ulster 3
Leinster (15 - 9) Isa Nacewa; Zane Kirchner, Ben Te'o, Ian Madigan, Luke Fitzgerald; Jonathan Sexton, Luke McGrath
(1 - 8) Jack McGrath, Sean Cronin, Tadhg Furlong, Devin Toner, Mike McCarthy, Rhys Ruddock, Josh van der Flier, Jamie Heaslip
Replacements (16 - 23) James Tracy, Peter Dooley, Marty Moore, Ross Molony, Dominic Ryan, Eoin Reddan, Noel Reid, Garry Ringrose
Ulster (15 - 9) Peter Nelson; Craig Gilroy, Darren Cave, Stuart McCloskey, Andrew Trimble; Paddy Jackson, Ruan Pienaar
(1 - 8) Kyle McCall, Rory Best (c), Wiehahn Herbst, Iain Henderson, Dan Tuohy, Robbie Diack, Sean Reidy, Nick Williams
Replacements (16 - 23) Rob Herring, Andrew Warwick, Ricky Lutton, Roger Wilson, Chris Henry, Paul Marshall, Ian Humphreys, Louis Ludik