The account, which involves co-ordinating and buying international campaigns and sponsorship, has been with Carat for five years.
Sources in local markets said the move is, in part, recognition of the fact OMD has tightened its grip on Vodafone's local market arrangements.
Carat's sister agency, Vizeum, recently lost the £120 million German Vodafone planning and buying account to OMD, which also plans and buys local media in the UK.
Carat continues to handle Vodafone's business in a number of local markets, including France. Some of the international activity that Carat has planned for Vodafone includes the sponsorship of CNN's Global Office.
Vodafone began to review its local media agency arrangements across Europe at the start of 2003. Some markets, including the UK, have yet to participate in this process.
The company recently revealed its association with David Beckham was coming to an end. The Real Madrid star has been the face of Vodafone Live!'s global activity for three years.
Stephen White, the new-business director of Carat International, said: "Changes are happening but Vodafone is still a client."
Nobody at OMD would comment on the move.