Carol singers and fresh snowfall greeted the prime minister and the Prince of Wales when they visited Birmingham's Queen Elizabeth Hospital.
Prince Charles last visited the £545m hospital with the Duchess of Cornwall in July, a month after it started admitting patients.
The two guests of honour arrived at about 1230 GMT and spent time talking to staff.
Currently 14 military service personnel are being treated at the hospital.
Prince Charles was also due to visit the Frankfurt Christmas Market to unveil the newly restored Edward VII statue in Centenary Square, Birmingham, on Wednesday, but the engagement was cancelled due to heavy snow forecast.