Gareth Holmes, the Perth Bears' General Manager of Football, will serve as interim chief executive until a permanent appointment is made.
The club's board has begun seeking a successor to Anthony De Ceglie, who resigned on Friday, Chairman Ben Morton said.
"Leading the newest club in the NRL is a great privilege, and we are confident we will attract outstanding candidates," Mr Morton said.
"the focus is on running a rigorous process that delivers the right leader for the next phase of the club's journey.
"Anthony played an important role in the successful start-up phase of the Bears, through record commercial partnership agreements and signing up 20,500 Foundation Members. The club thanks him for his contribution over the past 18 months.
"The work of the staff in WA continues, and the football program under Head Coach Mal Meninga is fully focused on welcoming the players and their families to Perth for an exciting new chapter for the Bears and the NRL.
"To the fans in WA and across the Nullarbor, thank you for your continued support."
Morton said the board aimed to find the right leader for the club's next stage.
Candidates can find application instructions on the Perth Bears' LinkedIn page.