Keshishian, who was formerly represented through BFCS before the production company's closure in June last year, has also directed commercials, including ads for Peugeot, Max Factor, MTV and Volkswagen, and has recently directed the latest pan-European spot for Bailey's, which will subsequently run in the UK. He also photographed campaigns for Coca-Cola and Faberge.
Keshishian, who has also worked with the Brave Film Company in the UK, was previously represented through Propaganda in the US.
As well as the In Bed With Madonna documentary-style film, which he made in 1991, Keshishian has made a number of pop videos for artists such as Elton John and Bobby Brown.
His signing comes as Spectre loses the director Pep Bosch to Rose Hackney Barber. Bosch has won more than 19 awards for his work, including a gold award at Cannes for the Volkswagen "amnesia" commercial. Bosch has also worked on spots for Fiat, Audi, BMW and Wrigley's Orbit.
The joint managing director of Rose Hackney Barber, Matthew Brown, said: "We are huge fans of Pep's quirky style of visual performance comedy. He has had enormous success in both the European and US markets and we look forward to mirroring this in the UK."