Mazzocchi made his
Serie C debut for
Pro Piacenza on 31 August 2014, in a game against
Grosseto. On 9 July 2018, he signed a four-year contract with
Serie B club
Perugia. On 25 January 2022, Mazzocchi joined
Serie A side
Salernitana on loan from league rivals
Venezia with a conditional obligation to buy. On 5 January 2024, Mazzocchi joined reigning Serie A champions
Napoli on a permanent deal, signing a three-and-a-half-year contract with the club. The transfer reportedly commanded a fee of about €3 million. It was the third-fastest send-off for a debuting player in the history of Serie A, behind only
Rolando Bianchi and
Francesco Cassata. ==International career==