Face masks will be required for all hospital patients and staff, as well as visitors, because the number of cases of Covid-19 has risen "significantly".
Health bosses announced that the rule will be in effect at all Cornwall's hospitals, treatment centres, and minor injury units starting Monday, July 4.
Two new sub-variants were cited for the increase in cases both locally and nationally. Services were already "under sustained stress"
This measure will be reviewed.
Royal Cornwall Hospitals NHS Trust said that there have been steady increases of healthcare staff positive for Covid-19. This has added to the strain on resources.
Kim O'Keeffe is the dual chief nurse of the trust and Cornwall Partnership NHS Foundation Trust (CFT). She stated: "Recently we've seen an increase in cases again. It's crucial that we use the tools available to help protect not just our patients but also our visitors and our colleagues."
"Making staff members wear masks is a decision that we made at a time we were already feeling pressure from the system.
She asked people to be kind to the staff who had been working so hard to protect patients during the pandemic.
The current policy of CFT and RCHT regarding visiting arrangements is unchanged.
Patients, staff, and visitors should continue to use soap and water, as well as the alcohol gel, to clean their hands.
Follow BBC News South West via Twitter, Facebook, and Instagram. Send your ideas and stories to firstname.lastname@example.org