Perth announced the departure of De Ceglie - former director of news and current affairs at Seven West Media after being editor-in-chief of the West Australian newspaper - in a press release on Friday evening.
AAP had been told by several well-connected sources in recent months that De Ceglie did not have the support of the board and that his tenure was not sustainable long-term, ahead of the Bears' entry to the competition in 2027.
The Australian Rugby League Commission (ARLC) owns the Bears franchise and the body's chairman Peter V'landys appointed De Ceglie.
V'landys was reported by News Corp to have given De Ceglie a virtual stay of execution in recent days and time to solidify his position.
Coach Mal Meninga, who has worked as a commentator for Fox Sports, was bemused by the reports.
"It's been an ongoing battle, it's him and I around who's going to get sacked next," Meninga told Fox Sports.
"I know I've got great support and Anthony has got great support, internally, so we just get on with our business.
"We can only control what we control and that's the internal things. We don't want to fight any external battles."
De Ceglie has ensured there will be no external or internal battles with his resignation as inaugural CEO, just weeks before the squad starts to prepare for the 2027 season.
"I'm extremely proud of what the hard-working Perth Bears team has achieved in the past year," De Ceglie said in the club statement.
"I have no doubt that the Perth Bears will continue to grow and grow, and become a behemoth of the national sporting stage.
"The club is in exceptional hands under the leadership of head coach Mal Meninga and assistant coach Ben Gardiner. Getting to work alongside both of them for the past year has been one of the greatest highlights of my professional life."
Perth's general manager of football Gareth Holmes will act as interim CEO, with the club to make public its future plans in coming days.
The appointment of a chief executive from a media background - before the club even had a board in place - was notable, given the NRL conceded it could face a battle for exposure in AFL-mad Perth.
De Ceglie had most recently been director of news and current affairs at Seven West Media, having been promoted after overseeing Western Australia's flagship newspaper.
AAP also understands that V'landys and the then-NRL chief Andrew Abdo met with Seven West Media chairman Kerry Stokes on the eve of the announcement that the competition would be expanded to include the Bears.
De Ceglie went into the job knowing the NRL's 18th side had work to do.
The local Seven West-owned newspaper The West Australian has been critical of the venture, which has been backed by state government cash.
"Normally if you're doing something right, you have a few critics along the way," De Ceglie said in June last year.
"I've been totally blown away by the amount of messages of people who want to get involved in the Perth Bears … I'm very optimistic this will be a huge success."
