Wales centre Scott Williams grabbed an early breakaway at the RDS Showground. But it was one-way traffic after that as Leinster hit back with six tries including a brace each for Rob Kearney and Ian Madigan.
Fly-half Madigan also converted all six tries in a 22-point haul though it was British Lions No8 Jamie Heaslip named man of the match as the holders bounced back from last week’s opening weekend loss at Glasgow.
For Scarlets, however, it was a second game without a win after a 32-32 draw with Ulster seven days earlier.
Kearney, back in the Leinster line-up, grabbed the opening try on nine minutes following delightful handling skills by Madiagan.
Williams pounced on a mistake by the home side in midfield and won the foot race for a try to level the scores.
But Kearney’s brilliant running soon had Leinster in control with a second try in the 27th minute and then a part in Madigan’s score.
Gareth Owen, a late call up after Liam Williams suffered a groin injury during the warm-up, denied Sean Cronin clinching a bonus point before half-time.
But Leinster capitalised on Phil John’s yellow card when Madigan touched down 12 minutes into the second half before Dominic Ryan followed against 14 men.
Tadhg Furlong barged over on 69 minutes before Johan Snyman claimed a late consolation score in injury-time after Heaslip was binned.
