Two tries from Vittoria Vecchini plus a score apiece from Valeria Fedrighi and Aura Muzzo was enough to seal victory despite a late scare from the hosts.
The game looked beyond the reach of Ireland despite a bright start that yielded a penalty try, while Neve Jones went over in the second half to keep them in touch.
But Katie Corrigan's intercept try with just a minute remaining on the clock set up a grandstand finish but the home side were ultimately unable to grab another score with the clock in the red and Italy held on for a deserved victory in Dublin.
IRELAND MAKE QUICK START
Ireland made the brighter start in Dublin, as Italy struggled to get out of their own half in the opening five minutes.
Beibhinn Parsons broke down the left and into the 22 from which Ireland ran the ball through the hands but were unable to convert five metres out.
But Italy could not clear their lines, however, and the hosts were straight back on the attack and found the breakthrough with just seven minutes on the clock.
Quick ball out wide from a scrum was too much for Italy to deal with, and Vittoria Ostuni Minuzzi's deliberate knock-on led to a yellow card and penalty try with Parsons primed to dot down.
The hosts remained in the ascendancy as they looked to take advantage of their good start and numerical advantage, and they almost did so as some nice footwork from Eve Higgins helped her side up the pitch but the Italian defence stood strong.
Parsons and Aoife Wafer then linked up down the left but Ireland were unable to find that final pass, with a number of knock-ons foiling promising attacks.
ITALY TAKE THEIR CHANCES
They were soon punished for their profligacy, as Italy grabbed a try on their first visit to the Ireland 22.
Concerted possession for the visitors eventually yielded a penalty, and the resulting lineout and maul could not be stopped to give Vecchini the simplest of finishes from close range.
That appeared to flip the half on its head, with Italy suddenly ascendant in search of a second try which came seven minutes later.
Parsons knocked on a long kick into the Ireland 22, which proved the platform for another Italian rolling maul.
This one was more effectively stopped in its tracks by Ireland, but that opened up space for Sara Tounesi to smash through three defenders before she was held up on the line but Fedrighi was on hand to dot down from the back of the ruck.
Ireland were suddenly causing themselves problems and Italy took advantage again to the tune of three points. Lauren Delany was caught trying to run the ball out from her own try-line and conceded a penalty for not releasing which her Sale Sharks teammate Beatrice Rigoni slotted home.
The sudden switch in the contest left Ireland reeling but they regrouped during the break and started the second half on the front foot, with Parsons almost sneaking her way through in the corner in the opening minute after a loose kick from Ilaria Arrighetti.
But Italy continued to show plenty of threat too, and Rigoni was almost sent through by a kick from Veronica Madia but the centre could not hold on with open space in front of her.
An end-to-end second half continued as Brittany Hogan almost found a way through in the corner for the hosts, after good work initially from Aoibheann Reilly.
The ball was eventually spread wide to Parsons in oceans of space out wide but she was unable to hold onto the pass.
ITALY TAKE CONTROL
It proved costly as Vecchini got her second try, and Italy's third, of the afternoon just minutes later.
It all came from a superb break by Alyssa D'Inca, who raced half the length of the pitch before being stopped by Enya Breen but the ball was quickly recycled through the forwards and Vecchini eventually powered her way over.
Ireland struck back immediately to maintain a glimmer of hope, as Neve Jones dived over from the back of a rolling maul.
But any momentum the hosts may have built up was vanquished minutes later as Muzzo sealed the bonus point and victory for Italy.
The wing was first denied her try by a forward pass from Madia but she was over the whitewash for good a minute later after excellent work from Rigoni to release her in the corner.
That appeared to put the game beyond doubt but a late try from Corrigan suddenly put the visitors on the backfoot and breathed new life into the hosts.
Corrigan excellently intercepted a pass from Rigoni and raced clear for her first international try and Ireland then marched straight back to the Italy 22 after kick off.
But despite intense pressure from the hosts, the Italian defence held strong to ensure they would be taking maximum points back home.
