Two tries from wing Morgan Stoddart helped the Scarlets seal a bonus-point 34-17 win over Aironi on Saturday.
The Scarlets were made to work hard for an hour before surging to victory in the closing stages.
Aironi had led 10-0 before the Scarlets came back, Stoddart's first score helping them to a 13-10 half-time lead.
It remained in the balance as Gabriel Pizarro put the hosts back in front but Nigel Davies' side held their nerve and pulled clear in the closing stages, with Stoddart rounding off the win.
Tito Tebaldi kicked the hosts in front from an early penalty but missed three more before the scrum-half's try and subsequent conversion put his side 10 points up after 27 minutes.
Scarlets fly-half Rhys Priestland had also missed the target with a ninth-minute place-kick but was successful four minutes after Tebaldi's try to cut the deficit.
And winger Stoddart touched down four minutes before half-time, Priestland converting and adding a drop goal in the last minute of the first half to send his side into the interval 13-10 to the good.
Another Priestland penalty stretched the margin to six points - but that was wiped out as centre Pizarro went over in the 56th minute and Tebaldi converted to put Aironi 17-16 up.
The Welsh side's response was almost immediate as Priestland added another three points on the hour mark. That settled their nerves and three tries in the final 11 minutes ensured they would complete an ultimately comfortable win.
Flanker Johnathan Edwards and centre Gareth Maule both crossed before Stoddart added his second a minute from time, Priestland missing all three conversions to complete a mixed day for kickers.
Tries: Tebaldi, Pizarro
Cons: Tebaldi 2
Tries: Stoddart 2, Edwards, Maule
Pens: Priestland 3
Aironi: 15 Julien Laharrague; 14 Giulio Toniolatti, 13 Matteo Pratichetti, 12 Gabriel Pizarro, 11 Rodd Penney; 10 James Marshall, 9 Michael Wilson; 1 Matias Aguero, 2 Roberto Santamaria, 3 Fabio Staibano; 4 Joshua Furno, 5 Marco Bortolami; 6 Josh Sole, 7 Simone Favaro, 8 Nick Williams.
Replacements: 16 Luigi Ferraro, 17 Luigi Milani, 18 Luca Redolfini, 19 George Fabio Biagi, 20 Gareth Krause, 21 Tito Tebaldi, 22 Paolo Buso, 23 Giulio Rubini.
Scarlets: 15 Daniel Evans, 14 Morgan Stoddart, 13 Gareth Maule, 12 Regan King, 11 Nick Reynolds, 10 Rhys Priestland, 9 Tavis Knoyle, 8 David Lyons (capt), 7 Johnathan Edwards, 6 Ben Morgan, 5 Dominic Day, 4 Lou Reed, 3 Peter Edwards, 2 Ken Owens, 1 Iestyn Thomas.
Replacements: 16 Emyr Phillips, 17 Phil John, 18 Simon Gardner, 19 Damian Welch, 20 Jonny Fa'amatuainu, 21 Martin Roberts, 22 Dan Newton, 23 Scott Williams.
Venue: Stadio Zaffanella
Referee: Andy Macpherson
Assistant Referees: Marius Mitrea, Matteo Liperini
Television match official: Stefano Mancini