People going to Royal Cornwall Hospital's A and E with minor injuries and ailments will be redirected to alternative services until after the New Year.
The change comes amid growing pressure on Truro's Emergency Department.
Susan Bracefield, the Director of Operations at the hospital trust, said: "We need our clinical teams to be able to focus on those who really need their specialist skills, so we’ve taken the decision to redirect patients to alternative services during the minor injury unit opening hours."
It will mean we can free up nurses and doctors to support those with serious and life-threatening emergencies and with speeding up discharge arrangements for patients who are ready to go home or to other care settings.
She added: "It’s vital that we maintain a safe service for everyone and there are a lot of people who come to us who can easily be seen and treated elsewhere."
People are being advised to travel to other minor injury units across Cornwall for the following conditions:
Sprains and strains
Minor burns and scalds
Head injuries (unless the injured person is unconscious)
Insect and animal bites and stings
Minor eye injuries
Bruising and grazes
Those who aren't sure if their injury is minor is advised to telephone their local unit before setting out to call NHS 111.
Cornwall's other minor injuries units which will be available are:
Bodmin Community Hospital - open until 10 pm
Camborne and Redruth Community Hospital - open until 10pm
Falmouth Community Hospital - open until 8pm
Helston Community Hospital - open until 8pm
Launceston Community Hospital - open until 8pm
Liskeard Community Hospital - open until 10pm
Newquay Community Hospital - open until 10pm
St Austell Community Hospital - open until 8pm
St Mary's Community Hospital, Isles of Scilly - open 24 hours
Stratton Community Hospital - open until 10pm
Stennack Surgery, St Ives - open until 8pm