Sandy Manson, who has held the role of CEO for 12 years, is to step down from 1 August and will become the group's new chairman and head of client service.
Andrew Walker, currently managing partner of the firm's Aberdeen office, will take the reins as chief executive from the appointed date.
The change of leadership is part of a long-term succession plan, which will see incumbent chairman Andrew Shepherd leave the position after eight years, although he is set to continue with the firm in a client facing role.
Walker has been a member of the Johnston Carmichael board for 11 years and has 23 years’ experience as a corporate financier, along with "a deep knowledge" of owner-managed businesses. He has taken the lead on the firm's digital strategy and the launch of its 12th office, which opened in Dundee earlier this month.
Walker said: “It is a great honour to take over the role of CEO from Sandy and build on Johnston Carmichael’s strong track record as Scotland’s leading independent accountancy firm.
“Our profession is going through a lot of change and we as a firm need to keep evolving, improving and investing to take advantage of the exciting opportunities which exist for a leading independent firm of our national scale."
Manson, who has overseen the firm's revenue growth from £18 million to £49m, said: “I have never been more positive and excited about the future of our firm and after 12 years now is the right time to hand on the baton to Andrew. With his considerable talents and experience, he will take this firm from strength to strength.
“I would also like to thank Andrew Shepherd for the immense contribution he has made to the growth and development of this firm in his eight years as chair.”
Johnston Carmichael now employs around 800 people across 12 locations.