Cesare Casadei was born on 10 January 2003 in Ravenna, Italy, and grew up in Milano Marittima. He began his football education at Cervia before joining Cesena, and when that club faced bankruptcy in 2018 he moved to Inter Milan's academy. He rose quickly through Inter's youth ranks, helping the Under-19 side win the Campionato Primavera 1 and earning a first-team call-up before leaving the club.
In August 2022, Chelsea signed Casadei from Inter Milan on a six-year contract for a reported fee of around €15 million plus add-ons. After loan spells at Reading and Leicester City — where he scored a 92nd-minute winner on his debut — he made his Chelsea senior debut as a substitute against Liverpool in January 2024. He was part of the Leicester City squad that won the EFL Championship in 2023–24.
His standout moment in international football came at the 2023 FIFA U-20 World Cup in Argentina, where he finished as the tournament's top scorer with seven goals and was named the Golden Ball winner as best player. Italy reached the final before losing to Uruguay. He was called up to the senior Italy squad for the 2024–25 UEFA Nations League quarter-final against Germany in March 2025.
A well-rounded, box-to-box midfielder comfortable in multiple roles across a midfield line, Casadei joined Serie A club Torino on a permanent transfer in February 2025, giving him his first sustained run of top-flight football in Italy.