Heading into the clash in Dublin looking to extend an undefeated run, Leinster fell behind after four minutes.
James Hume ran in a fantastic opener for Ulster, which was in the hunt for a first trophy since 2005-2006.
However, James Lowe quickly got Leinster on track, with any hopes of an Ulster comeback swiftly extinguished after the break.
Billy Burns's pass, which seemed to have been aimed at Marcell Coetzee, was gathered in by Robbie Henshaw, who burst over for Leinster's second, with Caelan Doris' score swinging the match firmly in the holder's favour.
It was enough to secure a 17th straight Pro14 win, with Leinster becoming the first side in the competition's history to take the title seven times and on three consecutive occasions.
With one piece of silverware secured, Leinster's focus will now switch to next weekend's Champions Cup quarter-final tie with Saracens.