Station improvement works will start in spring 2020 and will take around two years to complete.
The project has been on the cards for several years with Costain involved in the planning and design stages.
Stewart Wingate, Chief Executive Officer, Gatwick Airport said: “Gatwick has been transformed in recent years and the redesigned train station will take the airport’s redevelopment to the next level by providing a seamless transition between the airport and the station, more lifts, escalators and a doubling in the size of the concourse.
“The project is a fantastic example of the public and private sector working together to deliver a world-class transport hub.”
The renovation will be managed by Network Rail who have awarded the contract to Costain.
Alex Vaughan, Costain chief executive officer, said: “Costain’s extensive capability to deliver complex programmes, using leading edge smart technology, will ensure travellers are kept moving at every stage of the works, minimising disruption during this capacity-critical redevelopment.”
Gatwick Airport Ltd and Coast to Capital Local Enterprise Partnership are co-funding the project with £37m and £10m respectively.