Bartle Bogle Hegarty has won ITV's £20 million ad account after a three-way pitch against DDB London and Mother.
The final agencies were chosen from a shortlist of five, which also included Miles Calcraft Briginshaw Duffy and Dare (which handles ITV's digital account) and Beattie McGuinness Bungay.
The pitch was handled by the AAR and was called by David Pemsel, ITV's marketing director, who was promoted in January to replace Clare Salmon. M&C Saatchi, the incumbent on the business, was not asked to repitch.
The decision reunites BBH with ITV after a two-year hiatus. The agency handled the ITV business for three years, before resigning in 2005, two months after Salmon arrived as the marketing director.
BBH's resignation followed the appointment of M&C Saatchi to handle a project to evaluate the ITV brand.
Pemsel said: "We are two companies that have gone through fundamental change since we last worked together. BBH displayed brave strategic thinking, a more holistic capability and a size and creative ambition to match our own."
Ben Fennell, the BBH managing director, added: "ITV is a great British brand. It's also a fantastically creative brand and is going through an exciting period of reinvention."
As well as working in partnership with ITV Creative, the in-house agency that creates ITV's on-air work, BBH will create off-air ads and work with the marketing department on strategic development. The first campaign will appear in January to promote the 2008 schedule, which ITV hopes will herald a revival in its commercial fortunes.