Wilmont joined the agency when it launched in London four years ago and he says that he has not yet decided on his next move.
One of the agency's highlights during Wilmont's tenure was the Cannes Gold-Lion winning 'We Are David Bailey' campaign for Samsung.
Wilmont said: "Cheil has changed from a 60-person studio, to a 200-person creative company in the past four years. It's been an exhilarating ride, but it's now time for someone else to continue the journey."
Prior to Cheil UK, Wilmont was the chief idea architect at People Ideas & Culture for three years.
During his career, Wilmont has also worked at Y&R, Euro RSCG, Naked and Kirshenbaum Bond and Partners.
Matt Pye, the vice president and chief operating officer at Cheil UK, said: "Logan has been an integral part of the management team defining a new creative strategy, building an award winning team and supporting the next phase in Cheil’s development.
"We respect Logan’s decision to move on to other opportunities and we would like to thank him for his tireless efforts and wish him the very best in the future. We are now looking for his replacement."