The black, green and gold certainly put up a fight, as they did during a 27-22 defeat in Belfast in December, but errors opened the door for Ulster, and they walked through it.
Alex Mitchell's yellow card - his second in as many matches against Ulster - provided the space for Ulster to score their fourth try during the second half as their flawless Champions Cup campaign continued.
Saints had threatened at 19-13 down, but they were never in front in the game after conceding three preventable tries - all of which came from the home side's failure to gather the bouncing ball.
Boss Chris Boyd, banned for two games, watched on from the Barwell Stand as Phil Dowson and Sam Vesty took charge, but it wasn't to be a happy audition ahead of next season as Ulster prevailed.
Saints had gone into the game knowing only a win would do if they wanted to stand any realistic chance of qualification for the knockout stages ahead of next Sunday's trip to Racing 92.
But they were under early pressure and they couldn't hold out as Mitchell was unable to gather and Robert Baloucoune picked up before beating Tom Collins and George Furbank to score in the corner.
Nathan Doak missed the conversion but he was soon making amends with a try after Ulster had punished Saints in ruthless fashion on the counter-attack.
Rory Hutchinson chipped into space but he couldn't quite gather it and Ulster were away, with Baloucoune bamboozling the home defence before offloading brilliantly for Doak to dive over.
Doak converted and Saints were 12-0 down inside the opening 15 minutes, once again giving themselves a mountain to scale in Europe.
But the home side responded well and after a big break from Brandon Nansen, they applied enough pressure to win a penalty, which Dan Biggar landed.
Saints were playing with real tempo, refusing to be deterred by the concession of two early tries.
And the home side scored one of their own before the break as Courtney Lawes, who had led the team out on his 250th Saints appearance, pinched Ulster possession inside his own half and then Hutchinson and Collins combined superbly to send Biggar over.
Biggar added the gloss to a sensational score but Saints were hit with another sucker punch before the break.
Billy Burns chipped ahead and Biggar couldn't gather, allowing Mike Lowry to grab the ball and charge over the line.
Doak converted with the final kick of a frenetic first half, and Ulster led by nine points.
Biggar soon reduced the deficit to six with a penalty early in the second period and Saints then produced some big defence to thwart Ulster.
Mitchell was sin-binned for stopping Lowry illegally after the full-back flew towards the Saints line, but the hosts then won a big penalty after an Ulster tap and go.
Ulster did manage to score before Mitchell returned to the field though as Baloucoune was once again the catalyst, allowing Ethan McIlroy to send Lowry in for a bonus-point score.
Ian Madigan missed the conversion but Saints were now 11 points down with 18 minutes to go.
There was one late moment of glee for the home side as Hutchinson ran a lovely line and scored, with Furbank converting.
But that was only enough for a losing bonus point as Courtnall Skosan knocked on and Ulster kicked the ball out to confirm their win.
Saints: Furbank; Skosan, Litchfield, Hutchinson, Collins; Biggar (Freeman 68), Mitchell (James 77); Waller (Iyogun 60), Matavesi (Fish 71), Painter (Garside 71); Ribbans, Nansen (Ratuniyarawa 40); Lawes (Coles 64), Ludlam (c), Harrison (Augustus 56).
Ulster: Lowry; Baloucoune, Hume, S Moore, McIlroy; Burns (Madigan 56), Doak (Shanahan 59); Warwick (O'Sullivan 17), Herring, M Moore (O'Toole 58); O'Connor (c) (Carter 58), Treadwell; Rea (Jones 68), Timoney, Vermeulen.
Referee: Pierre Brousset