On 6 June 2018Western Sydney Wanderers announced that de Marigny was joining the club to take over the vacant assistant coach position. Following the sacking of head coachMarkus Babbel on 20 January 2020, de Marigny was named as the caretaker head coach for the club. He was released on 12 October 2020 after a statement was released by the club. His replacement was Carl Robinson.