The move comes after Victoria state last month said it would give additional time and funding to a separate Royal Commission that is probing Crown's operations in that state, to allow it to investigate a wider range of matters.
The ongoing inquiries into Crown are to assess its fitness for holding gambling licences in various Australian cities after media accused the company, one-third owned by billionaire James Packer, of ties to money laundering.
A final report from Western Australia was initially expected in mid-November, but will now be delivered on March 4, 2022.
"The state government believes that public interest will be best served if the Perth casino Royal Commission has sufficient time to produce its final report," Western Australia Premier Mark McGowan said.
A Royal Commission is Australia's most powerful type of public inquiry and has the power to compel witnesses.
(Reporting by Shashwat Awasthi; Editing by Christopher Cushing and Richard Pullin)