De Leo started his career working as a youth coach for regional teams from his native Campania such as Cavese and Nocerina.
[1] He successively worked as a technical collaborator for a number of coaches such as Roberto Mancini and Siniša Mihajlović.
[2] In 2012, De Leo rejoined Mihajlović's coaching staff, becoming a technical collaborator for the Serbia national football team, and following him also on his subsequent stints at Serie A teams Sampdoria, AC Milan, Torino and Bologna.
In 2023, De Leo obtained a UEFA Pro Licence at the renowned coaching school of Coverciano.
[3] On 13 January 2025, De Leo was unveiled as the new head coach of the Malta national football team.