After retiring as an active footballer, Gastadello accepted to stay at Brescia as a coaching staff member. On 7 December 2020, following the dismissal of
Diego López as a head coach, he was named the club's
interim head coach, overseeing a 2–2 draw against
Cremonese before moving back to his previous role following the appointment of
Davide Dionigi as new boss. On 21 December 2022, Gastaldello was sacked by Brescia with immediate effect following the dismissal of
Pep Clotet as head coach. He was however re-hired by Brescia on 20 February 2023, this time as the club's new head coach. Despite Brescia suffering relegation to Serie C following a defeat at the hands of
Cosenza, Gastaldello was confirmed in charge of the
Rondinelle for the new season; Brescia were successively readmitted to Serie B to fill a vacancy created by the exclusion of
Reggina. On 10 November 2023, following a string of negative results that left Brescia in 13th place in the Serie B league table, Gastaldello was however dismissed once again from his coaching post. On 18 June 2024, he was announced as the new head coach of Serie C club
Legnago Salus. He was sacked on 26 September 2024 after suffering six defeats in the first six league games of the season. ==Managerial statistics==