At Four he will be taking on a portfolio of consumer-focused clients and creating a new practice, building on Four's consumer technology and entertainment work.
He will work alongside other PR teams in property, financial services, travel and tourism, public sector, sport and the arts.
Redfern worked with two of Four's founding partners, Nan Williams and Ray Eglington, in the late 1990s at Charles Barker BSMG when Williams was its CEO and Eglington was joint MD.
Redfern also took over the running of Charles Barker BSMG's youth division, Slam, from another Four founding partner, Tim Lewis.
Since then he has taken on in-house EMEA marketing and PR roles with clients such as Mitsubishi Electric and worked with agencies including Joe Public Relations, PR21 and Ogilvy PR New York.
His client portfolio spans Dell, MTV, Carphone Warehouse, FujiFilm, British Nuclear Fuels, British American Racing, Orange and Zurich Financial Services, Diageo and Twentieth Century Fox.
Einir Williams, managing director, Four Communications, said: 'We are pleased to welcome such a highly experienced, motivated and commercially successful director such as Kevin into our PR division.
'This year is special for us as we enter our 10th year and we are focusing on investment in the business to take us to the next stage of growth.'