Ulster's hopes of securing a Pro12 play-off place suffered a potentially fatal blow with this home defeat by Leinster, who have already qualified.
Leinster led 13-8 at half-time thanks to a Kevin McLaughlin try and eight points from the boot of Jonny Sexton.
Johann Muller scored Ulster's try and Ruan Pienaar added a penalty but Sexton scored a drop goal after half-time.
Ulster trio Chris Henry, Paddy Wallace and Pedrie Wannenberg all came off with injuries during the match.
The extent of the injuries will be assessed in the coming days as Ulster prepare for next week's Heineken Cup semi-final against Edinburgh in Dublin.
Leinster dominated possession early on and showed the greater intensity at the breakdown as they set out to secure a clean sweep of six wins over the other Irish provinces this season.
Their endeavours were rewarded in the seventh minute when Dave Kearney made an initial thrust and passed to flanker McLaughlin, who dived over the line for a try.
Sexton converted to hand his side an early seven-point advantage.
Pienaar missed with his first penalty attempt but Muller gave Ulster hope with his first-ever try for the province on 25 minutes.
The South African lock was adjudged to have grounded the ball after accepting a good pass from Wallace, with Willie Faloon also having played his part in the build-up.
Scrum-half Pienaar was off-target with the conversion.
Sexton knocked over a penalty on the half hour and Pienaar and the Ireland fly-half then traded penalties before the break.
The home side enjoyed a bright spell at the start of the second half but were unable to make any inroads against a well organised Leinster defence.
Pienaar could not to reduce his side's deficit as he missed with another penalty effort.
Leinster enjoyed a period of sustained pressure in the final quarter of the game and a well executed drop goal by Sexton from in front of the posts ensured victory for the visitors.
The match represented Brian McLaughlin's final game in charge of Ulster at Ravenhill, and also the final appearance of back row Pedrie Wannenberg at the Belfast venue.
Ulster's record against Leinster now shows a disappointing return of one win in the last 17 encounters between the sides.
However attention will now quickly switch to next week's European semi-finals, with Ulster having reached the last four for the first time since 1999, and holders Leinster travelling to France to face Clermont Auvergne.
With that in mind, prop Declan Fitzpatrick came through the game unscathed following his lengthy absence through injury, and Paddy Jackson staked his claim for a starting place next week with an impressive display at fly-half.
Ulster: S Terblanche; A Trimble, D Cave, P Wallace, C Gilroy; P Jackson, R Pienaar; T Court, N Brady, D Fitzpatrick; J Muller (capt), L Stevenson; C Henry, W Faloon, P Wannenburg.
Replacements: A Kyricaou for Brady (60), P McAllister for Court (60), A Macklin for Fitzpatrick (55), N McComb for Wanneburg (49), R Diack for Henry (17), I Porter for Pienaar (67), I Humphreys for Trimble (75), A D'Arcy for Wallace (33).
Leinster: R Kearney; D Kearney, B O'Driscoll, F McFadden, L Fitzgerald; J Sexton, E Reddan; C Healy, R Strauss, M Ross; L Cullen (capt), B Thorn; K McLaughlin, D Ryan, S O'Brien.
Replacements: S Cronin for Strauss (61), H van der Merwe for Healy (55), N White for Ross (67), D Toner for Thorn (72), S Jennings for McLaughlin (60), I Boss for Reddan (55), I Madigan for Sexton (72), F Carr for Kearney (67).
Referee: John Lacey (IRFU)