After his retirement, he switched into a coaching staff role at Virtus Entella, serving as first team assistant and successively as youth coach. Under his guidance, the
Primavera Under-19 team managed to reach the final of the
Coppa Italia Primavera 2017, then lost to
Roma 3–1 on aggregate. On 30 April 2017, Castorina was promoted to the first team head coaching role until the end of the season after
Roberto Breda's dismissal following three consecutive losses in the
Serie B league which led Virtus Entella out of the promotion playoff zone. On 31 May 2017, Virtus Entella announced Castorina will serve as permanent head coach for the
2017–18 Serie B season. He was dismissed on 5 November 2017, due to poor results, and replaced by
Alfredo Aglietti. After his dismissal, he returned at Virtus Entella in 2018 as a youth coach, winning the
Campionato Nazionale Dante Berretti title in 2019. He left the club in May 2020, ending a thirteen-year tenure with the Ligurian club. ==References==