The force will be vacating the current site next month and relocating to new premises nearby while decommissioning works will be completed next Spring.
McLaren Living plans to submit proposals early next year for a new mixed-use neighbourhood of 300 build-to-rent homes and 30,000 sq ft of commercial space.
Matthew Biddle, managing director at McLaren Living, said: “We’re really excited to have acquired such a great site, in the commercial heart of Watford, close to local amenities and with excellent connections to London.
“We’re looking forward to working with Watford Borough Council and the local community on our plans for Clarendon Road, to deliver a mixed-use neighbourhood, bringing forward much needed new homes for rent, along with high-quality commercial space.”
David Lloyd, the Police & Crime Commissioner for Hertfordshire, added: “I am pleased to see this conditional sale has exchanged, and once completed will generate additional funding for the constabulary.
“The station on that site had reached the end of its economic life and it was no longer fit for purpose for the demands of officers and staff. Watford now has a new thoroughly modern police station in the town centre at 3 George Street.”