Work on a £9m multi-storey car park is to start at Gloucestershire Royal Hospital in Gloucester in April.
A specialist parking operator is building the 1,000-space car park for Gloucestershire Hospitals NHS Foundation Trust.
Another 400-space multi-storey car park at Cheltenham General Hospital is also proposed, subject to a planning application which is at appeal stage.
Some staff said they feared the cost of parking at work would increase.
Vinci Park, which is designing and building the facilities, took over the management of the existing car parks at both hospitals on 4 January.
Cheltenham's planning committee turned the application for the 400-space car park down in May 2009 because of the proposed use of timber cladding.
The NHS trust has launched an appeal.
If planning permission is granted, the car park at Cheltenham hospital will cost Vinci Park a further £6m.
Following development, the company said it will manage both sites the next for 30 years.
A trust spokeswoman said the trust already "heavily subsidises" alternative travel such as a free park and ride and free and subsidised bus services.
"However, demand was still high for staff car park provision and it was decided that the only way forward was to seek an experienced private sector firm which could fund the capital cost of the improved car park provision as well as run our car parks fairly and effectively," she added.
"Progress on the implementation of these arrangements was reported to and discussed at our Green Transport Group, which includes staff representatives."
She said staff have been asked to apply for parking permits, which are related to their salary and there will be an additional charge of 50p per day from April.
The trust's Graham Lloyd said: "The increase is necessary to cover the costs associated with the new parking arrangements."
Parking charges for members of the public will remain unchanged, the spokeswoman added.