The decision comes after a string of poor results, including a defeat to Philadelphia Union, who had been winless prior to the encounter.
Montreal have managed just one victory in their opening seven matches, leaving them second from bottom in the Eastern Conference standings.
"CF Montréal Managing Director of Recruitment and Sporting Methodology Luca Saputo has announced that Marco Donadel has been relieved of his head coaching duties effective today," the club said in a statement.
"Philippe Eullaffroy will assume the team's head coaching responsibilities until a permanent head coach is hired."
Donadel’s departure means the club will once again search for a new manager just six months after confirming him in the role.
He was appointed permanently in October after initially stepping in as interim boss in March 2025, replacing Laurent Courtois