Staff at West Suffolk Hospital will be expected to leave their cars at home for one day a week from July 1.
They are instead being asked to find alternative ways of getting to work as part of the car-free day scheme, which aims to reduce parking problems at the hospital.
Bosses estimate the move will reduce cars on the site by 200.
An electronic system will allow staff to choose which day they would like.
However, some staff have voiced their concerns about the move.
Graham Kendall, secretary of the Bury and district health branch of the union Unison, said: “One worry is about not being able to get into work. It’s a job to find someone to car share who works the same shift. We’re in consultation with the trust about it and all the concerns have been raised.”
Jan Bloomfield, executive director of workforce and communications at the hospital, said: “Demand for staff car parking spaces continues to outweigh supply.
“We have looked carefully at all the options for resolving this issue and feel the car-free day offers the fairest solution.”
She said measures had been introduced to give staff choice as to how they get to work including parking at the rugby club and using a free shuttle bus as well as a car share scheme with dedicated parking spaces for those taking part.