The appointment marks a return to the UK for Baker following a two-year stint in the US where he was the managing director of the viral marketing agency BzzAgent.
Before that, he spent two years at Proximity London as its head of digital services.
He has also worked as a partner at Agency.com and was a founder of Organic.
Baker's appointment at OgilvyOne Interactive fills the gap created by the promotion of Louise Ainsworth, who takes on the new role of head of strategy and planning.
Baker will share client services responsibilities with Sam Williams-Thomas.
Mike Dodds, the OgilvyOne joint managing director, said: "John is a huge coup for OgilvyOne and he joins at a time of huge digital growth."
Interactive is now more than 25 per cent of our overall business and we believe it could represent more than 50 per cent in a year or so. Last year we doubled our Unilever business with work for Sunsilk and Knorr and this year we expect to exceed this significantly."