The mail delivery giant said the new contract does not affect its fleet of red delivery trucks and vans, as they remain in-house.
It has signed a three-year deal for an undisclosed sum with LeasePlan as part of an initiative to reduce costs and return to profitability. LeasePlan will provide a range of services including procurement, administration, maintenance, repairs and disposal as part of the contract.
Royal Mail's project director Peter Restarick said: 'Quite simply this is good housekeeping and, by reducing costs, is another important step in our renewal plan. I'm confident LeasePlan will provide a superb level of expertise and professional support.'
LeasePlan UK's managing director Kevin McNally added: 'We are delighted to have been selected by Royal Mail and we will work hard to meet its needs to help it reduce costs and further improve the service.'