David Kearney and Ian McKinley scored tries either side of half-time for Leinster, with Treviso flanker Gonzalo Padro dotting down in first half injury-time.
The Italians survived the sin-binning of lock Corniel van Zyl but leaked a late try to Leinster winger Andrew Conway, which Nacewa converted for a 25-point winning margin.
It was a deserved victory for Joe Schmidt's men, who lost 29-13 away to Treviso in September. The result also got the province back on track after their 11-3 defeat to the Cardiff Blues last time out.
Treviso's New Zealand-born full back Joe Maddock caused Leinster's defence a great deal of worry early on, but winger Benjamin de Jager was unable to supply the finish in the corner.
Nacewa landed three successful penalties in the opening 15 minutes, with Treviso out-half Willem de Waal missing two difficult efforts.
In the 28th minute, Leinster finally made the try-scoring breakthrough. Out-half McKinley skipped away from de Waal's attempted tackle and his timely offload sent Kearney stepping inside Maddock to score by the posts. Nacewa converted for a 16-0 lead.
Treviso kept hammering away and got their reward after building pressure through their forwards. de Waal kicked a penalty to touch and although Leinster initially held out, a subsequent drive from close range saw Padro crash over in the left corner for an unconverted score.
Padro was part of a strong Treviso pack, with players like skipper Antonio Pavanello, hooker Enrico Ceccato and number 8 Marco Filippucci putting in busy shifts. Filippucci also had a try ruled out for a forward pass.
However, Leinster, who were 16-5 ahead at the break, put the result beyond doubt with a superb 46th minute try.
Dominic Ryan led a counter attack, and Isaac Boss, McKinley, Nacewa and Kearney were all involved as they gained ground. Kearney's neat pass saw McKinley jink past the final defender to score to the left of the posts. Nacewa again added the extras.
The game ended as a contest in the 56th minute when van Zyl was yellow carded for persistent infringing in the ruck.
But problems at set piece time prevented Leinster from converting pressure into further points. They had a try ruled out for a forward pass from hooker Richardt Strauss, just as Kearney looked set to score his second of the night.
The third try finally came in injury-time with Conway touching down in the right corner after a long pass from Ian Madigan was flicked on by fellow replacement Niall Morris.
Speaking afterwards, man-of-the-match Eoin O'Malley said: "I think that towards the end we probably could have got the bonus point, but Treviso are a very strong side and really put it up to us.
"On reflection, I think we tried to force it a bit at the end and that's something for us to work on towards the end.
"We knew how important it was to get the win coming into the match, especially in front of the RDS crowd, and it really sets up next week's game (at home to the Scarlets) which is going to be huge."
|Leinster Rugby Score Card|
|Benetton Treviso Score Card|