The introduction of parking charges at Glan Clwyd Hospital, Bodelwyddan, has been delayed at the last minute.
Staff voiced their opposition at a protest in August
The controversial fees were due to be brought in from Monday.
Managers said the delay for patients and visitors for a week was to let them get used to the idea, and for staff for three months for talks under a health trust grievance procedure.
Conwy and Denbighshire NHS Trust said the scheme was necessary to ease traffic congestion at the site.
Public service union Unison is balloting members on whether they want to take action, such as a work to rule, over proposals described by regional organiser Geoff Edkins, as "outrageous."
"It's wrong to charge the sick and people who are visiting the sick and it's equally wrong to charge people to come to work," said Mr Edkins.
He said staff earning less than £15,000 a year would be charged £50 a year to park while higher earners would pay £100 a year. But except for priority users, paying £200, there was no guarantee of a parking place.
Patients and visitors face charges of £1 for an hour, and £5 for six hours.
He said: "I know there are charges at other hospitals, but here you have to use your car to get to work because there's no proper bus service."
The union wants the hospital to look at alternatives, such as providing buses for staff or improved cycling facilities.
The results of the Unison ballot will be announced on Tuesday, 11 October, and other unions are also consulting members.
Hospital spokeswoman Kay Hemsley said a delay would allow staff from the company to talk to patients and visitors and explain how it worked.
The decision was taken after the unions had invoked the grievance procedure to allow more consultations.
"We are hoping that with a longer lead-in time, we'll be able to give more reassurance to the public," she said.
"The demand for car park spaces keeps increasing and congestion has made it difficult on occasions for ambulances to access the site and for patients to attend their appointments."
The trust said that with cars blocking access routes and an expected 40% increase in traffic over the next three years there was a need for action.
The trust said the substantial costs needed to be funded, as it could not be taken from money intended for patient care.