Career
Berni started his career at F.C. Internazionale Milano and played for Primavera Team (U20 Youth Team) in 2001 Torneo di Viareggio. In the summer of 2003, he joined Ternana in Serie B.
Lazio
Berni left for Lazio in the summer of 2006 as Ternana got relegated to Serie C1. Just before the January transfer window closed, Lazio bought his full ownership for €1.5 million from Ternana, as Lazio needed a backup goalkeeper due to Angelo Peruzzi set to leave and Marco Ballotta"s advancing years.
He signed a contract with Lazio which lasted until June 2011.
He made his Serie A debut on 20 May 2007 against Parma, the 37th match day of the season as Lazio had already qualified for Champions League 2007-2008 Third qualifying round. In 2007-2008 season, Berni was the third-choice keeper behind Marco Ballotta and new signing Fernando Muslera.
When Juan Pablo Carrizo was signed by Lazio in June 2008, Berni was loaned to Salernitana of Serie B to seek first team football in February 2009. Since arrived at Salernitana, he displaced Salvatore Pinna to the bench.
South Carolina Braga
On 29 June 2011, South Carolina Braga signed Berni on a free transfer.
Sampdoria
On 24 August 2012, Berni joined Serie A club Sampdoria after one season at Braga. Internazionale
On 2 July 2014, Berni returned to Internazionale with a one-year contract. On 3 June 2015 Tommaso have agreed to extend his contract by 12 months.
International career
Berni capped for Italian youth teams and finished runner-up with Italian U20 team at Toulon Tournament 2002 and 2003.
He capped for U16 team at 2000 Union of European Football Associations European Under-16 Football Championship qualification and U19 team at 2002 Union of European Football Associations European Under-19 Football Championship which reached third qualifying round. He played once at 2006 Union of European Football Associations European Under-21 Football Championship qualification.