McGrath chief executive Cameron Judson and all but one of the real estate firm's directors are leaving after the company issued another earnings warning.
Chair Cass O'Connor and three other directors are also stepping down, leaving founder John McGrath as the only survivor. He'll be interim executive chairman.
McGrath on Monday said Mr Judson and head of corporate services Morgan Sloper are leaving because the company, which has struggled since listing on the ASX in December 2015, no longer requires expertise in organic growth or merger and acquisitions.
"Cameron and Morgan were engaged when we anticipated a higher volume of corporate activity," Ms O'Connor said.
"Their skill sets are broader than the company currently needs."
Mr Judson was originally appointed in July 2016 to work alongside Mr McGrath as joint CEO before assuming full control just weeks later.
The announcement that Mr Judson, Ms O'Conner, Mr Sloper and directors Elizabeth Crouch, Nigel Dews and Cath Rogers will leave came as McGrath said it expects full-year earnings before interest, tax, depreciation and amortisation of between $5.8 million and $6.8 million
McGrath had already said it did not expect to meet analysts' expectations of $16.6 million in EBITDA amid slower-than-expected sales, particularly at its company-owned agencies.
Its shares plunged on the news and closed down 8.0 cents, or 13.8 per cent, at 50 cents.
That's less than a quarter of their $2.10 price ahead of McGrath's market listing in December 2015, with Monday's earnings warning the third since then.
Agent departures and restrictions on foreign ownership have hit the agency, which in November was rumoured to be considering delisting from the ASX.
