The deal will see Arval solely funding and managing most of Serco's company fleet of 1,200 cars and almost 1,000 LCVs.
Arval will finance the vehicles on contract hire and will provide Serco with a maintenance and repair service, accident management and driver services. It will also provide fuel management using its AllStar fuel card.
Paul Manning, director of shared services at Serco, said: 'Through this contract we have been able to consolidate the number of vehicle leasing companies we use across the group.
'During the competitive tender, the Arval PHH team was able to obtain improved terms from many key suppliers and therefore demonstrated the added value that we expected from a large fleet management company. We will also be using the InterActive platform to manage our fuel and fleet operations online. The system was another key element of Arval PHH's success in the tender.'
The deal involved Arval PHH working with Serco to negotiate a sole supply deal with Ford.
Arval PHH UK strategic sales manager Andrew Goodwin said: 'The key to this contract was being able to offer a comprehensive yet bespoke solution. Our consultative approach enabled us to focus on areas that were most important to Serco, such as cost reduction, policy control and better visibility of information.'