The £12 million scheme will create extra spaces to help pave the way for future developments on the busy hospital site.
Peter Welsh, the hospital’s General Manager, said plans were in place to minimise disruption.
He said: “This is a very important development for the hospital which will create a new modern parking facility for patients, visitors and staff and also open up the possibility of further developments at the hospital.”
The new multi-deck car park will add an extra 150 car parking spaces, providing 1,120 on site in total, and will also create 85 construction jobs.
It will also allow Cardiff and Vale University Health Board to progress its work with the Welsh Government and the Vale of Glamorgan Council on developing a new Adult Mental Health Unit on the site.
The 135-bed unit, which is currently in the planning process, would be built on the site of the existing car park opposite the hospital’s main entrance.
It would bring together a range of specialist services on one site in modern tailor made facilities.
Geoff Walsh, the UHB’s Assistant Director of Planning, said work was already underway on the car park and was expected to be completed by September 2013.
He said: “The new car park will be a boost for the hospital and hopefully lead to other exciting developments.
“There may be some disruption on the site during construction but we’re working on a number of ideas to minimise that. As part of the planning application we have permission to create a dedicated entrance for construction traffic at the Merry Harriers interchange which should help to reduce the impact of the work on those working and visiting the hospital.
“University Hospital Llandough has benefitted from millions of pounds of Welsh Government investment in recent years and the car park could be the catalyst for more to come.”