De Marigny became Victory assistant coach in 2013 after moving from Marconi Stallions and has now decided to return home to Sydney to be with family.
"It was a difficult decision to leave Melbourne Victory after such a successful season but I have family commitments in Sydney that I need to put first," De Marigny said.
"I specifically want to thank Kevin for the opportunity to work with him at such a professional club and also to the Chairman, Board of Directors, players and staff for making me feel so welcome."
Mautone had been with Victory for nine years and revealed that decision to leave was made with great sadness.
"With the ever-growing commitment this job requires, my decision is purely based on me wanting to spend more time with my young family," Mautone said.
"In my nine years at Melbourne Victory, I have worked with a lot of great people and I want to take this opportunity to thank the chairman, board of directors, Kevin and everyone associated with the club for making my time at Melbourne Victory such a memorable one.
"I wish Kevin and the team all the best for next season and beyond."