De Leo was born on October 25, 1995, in La Mirada, California, U.S.[1] to parents John and Janie who own a wholesale plumbing supply company.

[4] As a youth, De Leo played for the Los Angeles Selects minor ice hockey team, where he was a teammate of Eric Comrie.

[6] After meeting Joe Sakic, Peter Forsberg, and Patrick Roy, De Leo chose to pursue ice hockey as a career.

[9] As an impending restricted free agent following the 2017–18 season, De Leo was traded by the Jets to the Anaheim Ducks in exchange for Nic Kerdiles on June 30, 2018.

[12] Following three years within the Ducks organization, De Leo left as a free agent and was signed to a one-year, two-way contract with the New Jersey Devils on July 29, 2021.

[14] After a lone season with the Devils, De Leo as a free agent opted to return to his former club, the Anaheim Ducks, by signing a two-year, two-way contract on July 14, 2022.

[16] After finding themselves in last place in the KHL, Barys Astrana began releasing expensive foreign-born players from their contracts in an attempt to cut costs.

[19] In returning to North America as a free agent, De Leo was later signed to a AHL contract for the remainder of the season with the Charlotte Checkers.