Ikon CEO Dan Johns has quit the agency after more than a decade following the announcement founder Simon White is stepping back into a chairman role.
White is taking up a newly created role of chairman, overseeing Ikon and fellow STW media agency Bohemia, targeting new acquisitions and with an eye on international growth.
In a statement STW said Johns was looking at "other business options" and did not rule him out of a new venture with the group.
Ikon has undergone several personnel shake ups recently, losing Sydney joint-MD Annick Perrin to Initiative, trading director Nicole Turley to rivals Starcom, and communications director Tom Rankin to UM, hiring a new chief operating officer Chris Graham in January.
White said: "Dan has done a great job at creating a truly national approach at Ikon, bringing teams across offices together and setting up new ways of doing business.
"He goes with our best wishes and thanks, we are looking forward to the next chapter after Ikon with Dan.”
Ikon Sydney managing director Pat Crowley will take on the role of acting CEO whilst the hunt is carried out for a successor to Johns.
White, who founded Ikon in 1999, and then sold to STW in 2010, added: "I am particularly excited about the opportunity for Ikon to now evolve and grow as it accelerates its capabilities as a leader in the new media world.