Leinster earn Irish bragging rights
Tries from Jordan Larmour and Luke McGrath proved crucial for the visitors, who continue to build momentum following a superb European break and will be full of confidence ahead of Friday's crucial trip to Glasgow Warriors.
Ulster fall to their second defeat in three matches following a surprise loss to Zebre last month, although they can take heart from the battling display.
Aaron Cairns impressed on his debut at scrumhalf, while hooker Rory Best made his first start of the season to bolster Ulster's pack.
However, Leinster hit the front after just seven minutes when Lamour scampered down the wing to score a memorable try.
Ulster increased the pressure, dominating territory and possession but Leinster's defence – marshalled by the superb Devin Toner – kept them at bay.
A pair of Ross Byrne penalties put Leinster ahead by three points at the break with Australian Christian Lealiifano kicking one for the home side.
And Ulster sensed a change in the wind 15 minutes into the second half when Dave Kearney was yellow carded for a deliberate knock on.
However, Leinster struck a fatal blow to Ulster's chances by extending their lead beyond a single score with a crucial try.
An Ulster knock-on was capitalised on and Luke McGrath crossed just three minutes after Kearney’s yellow with a dart in the corner.
Ulster upped the tempo, pinning Leinster back inside their own half as they searched for a way back into the game.
But it was again Leinster that almost scored when Jordi Murphy latched onto the end of an overthrown line-out ten metres out.
Ulster's charge fizzled out in the final ten minutes and Leinster finished things off as McGrath crashed over for his second of the match.
That secured the win, the first for an away side in this fixture in nine attempts and the first for the Dublin-side in Belfast since 2014.
Tries: Larmour, McGrath 2
Cons: Byrne, Marsh
Pens: Byrne 2
Ulster: 15 Charles Piutau, 14 Tommy Bowe, 13 Luke Marshall, 12 Stuart McCloskey, 11 Jacob Stockdale, 10 Christian Lealiifano, 9 Aaron Cairns, 8 Jean Deysel, 7 Chris Henry, 6 Sean Reidy, 5 Iain Henderson (captain), 4 Alan O'Connor, 3 Rodney Ah You, 2 Rory Best, 1 Callum Black,
Replacements: 16 Rob Herring, 17 Andy Warwick, 18 Ross Kane, 19 Kieran Treadwell, 20 Robbie Diack, 21 Jonny Stewart, 22 Peter Nelson, 23 Louis Ludik.
Leinster: 15 Rob Kearney, 14 Adam Byrne, 13 Rory O’Loughlin, 12 Noel Reid, 11 Dave Kearney, 10 Ross Byrne, 9 Jamison Gibson-Park, 8 Seán O’Brien (captain), 7 Jordi Murphy, 6 Dan Leavy, 5 James Ryan, 4 Devin Toner, 3 Tadhg Furlong, 2 James Tracy, 1 Jack McGrath.
Replacements: 16 Richardt Strauss, 17 Cian Healy, 18 Andrew Porter, 19 Ross Molony, 20 Jack Conan, 21 Luke McGrath, 22 Cathal Marsh, 23 Jordan Larmour.
Referee: John Lacey
Assistant referees: Craig Evans, Leo Colgan
TMO: Olly Hodges