Barreto grew up in the youth ranks of Treviso. In 2002, he was loaned to A.C. Milan where he was part of the Allievi Nazionale side that won that year's, defeating Fiorentina in the final.
After scoring 12 goals in the 2004–05 season for Treviso, he was signed by Udinese, who gave him the opportunity to mark his debut not only in the Italian top flight but also in European competition, in which he scored two goals against RC Lens during the 2005–06 UEFA Cup.
Loan to Treviso
He returned to Treviso on loan in 2007, scoring 14 goals in 2007–08.
Barreto spent the 2008–09 season on loan at Bari, with whom he scored his first hat-trick in Serie B on 21 April 2009 during a match with Ancona. He contributed 23 goals during the season that saw Bari crowned Serie B champions, under Antonio Conte. In 2009–10 season, his loan was extended and his goal scoring made Bari impress in the first half of the Serie A season. However, after the injury of centre-back Andrea Ranocchia and his striking partner Vitaly Kutuzov, the team performance also slipped. On 25 June 2010, Bari signed him in a co-ownership bid, for €4.5 million. In the next season, despite Kutuzov was recovered from injury, the team saw the departures of Italian international centre-backs Andrea Ranocchia and Leonardo Bonucci. With the failure to sign important replacements, not only for the centre-backs, the team conceded more goals and their tactics where affected. Barreto scored 4 goals before the winter break as team top-scorer, however much lesser than his performance last Christmas. The team finished as the bottom to enter the winter break. Barreto also injured in November, the match against Parma. He injured again after came out from injury in December, against Palermo.
On 24 June 2011, his contract was redeemed by Udinese for €3 million, with whom he only played 12 games. On 17 January 2013, Torino purchased him for €1.8 million from Udinese in another co-ownership deal, in a 2½year contract. Here, he found Giampiero Ventura, his coach at Bari. He debuted for the Granata on 20 January in an away fixture against Pescara won by Torino 2–0. He scored his first goal with Torino on 30 March against Napoli at the Stadio Olimpico, his first goal in 874 days. He scored again in the next week away to Bologna, scoring the momentary 0–1. He ended the season with 16 appearances and three goals and on 19 June the co-ownership between the Friuli and Turin was renewed. In June 2014 Torino redeemed his entire contract in a blind auction, for an additional €859,000.
