Farmer was director of marketing communications at Freeview, where he was responsible for the relaunch of Freeview+, the digital recording service, in a campaign starring Gordon Ramsay, Alan Carr and some of the 'Coronation Street' cast, created by Beattie McGuinness Bungay.
He has a background in advertising, having worked at CHI & Partners and Bartle Bogle Hegarty before joining Freeview.
Farmer's new job will see him look after marketing all the programming on ITV1, ITV2, ITV3 and ITV4 on-air and off-air through paid media.
He will also oversee the strategic and creative development of the channel brands, including the extension of content and on to new platforms such as Freeview and Freesat.
ITV has recently began a big campaign to promote digital channel ITV2, featuring the stars of some of its programmes, including Katie Price and Peter Andre.
Farmer said: "I am delighted to be joining ITV's marketing team at an exciting and significant time in the development of its marketing and branding strategy and I am looking forward to bringing my passion and experience of consumer communication to ITV."
He reports to David Pemsel, ITV's group marketing director.