Analysts at City broker Liberum said the news was “disappointing”.
Hopkins, who has been Workspace’s chief executive since 2012, will step down on 31 May.
Chief financial officer Graham Clemett will then take over as interim boss until the appointment of a permanent successor, the search for whom is to start shortly.
“On behalf of the board, I would like to thank Jamie for his significant contribution as chief executive of Workspace over the last seven years,” said chairman Daniel Kitchen.
“Workspace has a strong senior management team and the board is confident that the business will be in good hands while the search for a new chief executive is underway.”
Hopkins, who will remain a shareholder, added: “After a superb seven years at Workspace, I have decided to step down. My decision to leave has been made purely on personal grounds.”
In a brief update, the FTSE 250 group, which owns and manages 65 offices around London, said it was trading in line with expectations. It will report its half-year results on 5 June.
Workspace shares dropped 0.2% to 979p in early deals on Tuesday.