Essential improvement works to St Mary’s Hospital are expected to start next week.
Work taking place includes fire safety improvements, roof maintenance and the replacement of water storage tanks, which will result in "a better patient experience".
The work is scheduled to begin on November 5th and is expected to be completed by January 14th 2019.
Cornwall Partnership NHS Foundation Trust said: "As bed capacity will reduce during the works, measures have been put in place to ensure business as usual continues in the hospital.
"Hospital staff will be working hard to ensure services run as normal, although on a reduced scale."
The hospital’s Minor Injury Unit will continue to run 24 hours a day, seven days a week, with x-rays available on Wednesdays.
Patients are asked to call 01720 422392 to confirm x-ray times before making their journey.
Ian Bartlett, Associate Director of Estates and Facilities for the Cornwall Partnership NHS Foundation Trust, commented: "Every effort will be made to minimise disruption while this essential work is carried out. We would like to apologise to anyone who is inconvenienced while this work is taking place.
"The end result will achieve significant improvements that will be of benefit to both patients and staff. All the patient area work will be completed in time for business as usual to resume in January following the Christmas holiday period."