Property assets consultancy BK will use the council's IT systems and 'hot-desk space' to integrate with the in-house property team.
If successful, the deal could have wider implications for councils.
A statement from the firm said: 'The council will be able to tap into the complete range of BK property skills. The council will also be able to call on specific expertise on a flexible basis rather than having to retain a large property team in house.'
The contract will run for three years, with an option to extend for a further two if it is successful. It involves 1,000 properties with an asset value of more than£600m.
Warwickshire's property services director Peter Ridley said: 'This new approach provides the county council with greater flexibility and access to a wide range of expertise through BK.
'As a number of posts became vacant in the department, we took the opportunity to try this new initiative.
'Rather than simply recruit new staff, we decided to work with a partner agency so we could combine our extensive knowledge and provide best value services.'
Head of BK's public sector division Angus Mylles said best value has forced councils to take a critical look at their property assets.