On 17 August 2012 Piatti signed for the Argentine club San Lorenzo de Almagro for a reported fee of €1 million.

[2] On 2 July 2014, Piatti signed a transfer agreement with Canadian club Montreal Impact of Major League Soccer.

He started all six games in the 2014–15 CONCACAF Champions League Championship Stage and helped the team reach the final, where they lost out against Mexican giants Club América, recording two goals and one assist in 526 minutes played.

[6] A dynamic attacker,[7] Piatti is a technically skilled dribbler, who is capable of both creating and scoring goals, and is able to play in several midfield roles.

Piatti paid tribute to him by lifting his jersey to reveal the message ‘Abuelo te amo’, which translates to 'Grandfather, I love you', on a couple of occasions, most notably at Estadio Azteca after he scored the opener in the first leg of the CONCACAF Champions League Finals.