Varley will also become a board director at the agency and is expected to receive a stake in the business, which was launched in 1994 by its managing partners, Andy Jeal and David Lucas.
Varley joined Walker Media in 2002 as a director on the Dixons Stores Group account. He previously worked with the Walker Media founding partner, Phil Georgiadis, at WCRS in the 80s.
Before joining Walker Media, Varley founded the digital start-up Oxigen in 2000. He has also held a number of senior positions at OMD and Carat.
Jeal said: "Varley fits our culture very well. He has the right mix of planning skills and commerciality, which is where we are as a business. We looked at a lot of people in the communications planning world but I'm not sure many were commercial enough."
Varley will head the agency's strategic and communications planning department.
He will also be charged with refining its planning model, which last year was split into investment, strategy and management.
Jeal added: "We have always believed that our service, thinking and performance is equal to, if not better than, that available elsewhere in the UK. This appointment is testament to our commitment to providing an even better product to our clients."