Phillips will be executive creative director of Golley Slater Advertising London and Golley Slater Digital from September 1.
Phillips has worked in advertising for over 15 years holding senior creative positions at London agencies including Euro RSCG Network, Delaney Lund Know Warren and Tequila/TBWA.
Phillips has worked across a range of high-profile brands including Vauxhall, Smirnoff vodka, Coca-Cola, Guinness, Halifax, Evian and EBay.
He then took a break in 2006 to create the strategy and creatively oversee the launch of a new mobile youth product, which was sold overseas.
Phillips said: "The Golley Slater role was too exciting to turn down. Creatively the agency is producing some cracking work. Golley Slater's latest army ads are receiving some great reviews."
The agency, which has 11 UK offices, has made a number of strategic appointments in the past few months including former Saatchi & Saatchi finance director and WPP Brand Union global chief operating officer Roy Powell. Commercial director John Kinder was also promoted to managing director of Golley Slater Digital.
Chris Lovell, CEO of Golley Slater, said: "Mip, Roy and John's appointments demonstrate our ambitions and our intent. We have taken our time in making these appointments.
"We are creating something special in London, which mirrors culturally our success across the other Golley Slater offices and disciplines in the UK."