He is facing a charge of threatening to kill/do grievous bodily harm.
A witness said a man came into the hospital's outpatients' building and threatened to shoot someone, Star News reported.
Canterbury District Health Board chief executive Dr Peter Bramley said police were called to an incident involving a patient at the Outpatients building on the Christchurch Hospital campus earlier this morning.
The incident has now been resolved and roadblocks are no longer in place.