Nick Medlin, 57, died from a head injury outside a pub in Pier Street, Ventnor, Isle of Wight, during a night out.
Michael Hudson, 32, from the Nottingham area but of no fixed address, appeared at Winchester Crown Court.
He was remanded in custody ahead of a trial, scheduled to last two weeks from 26 June.
Mr Medlin, a father-of-two from Ventnor, worked at HMP Parkhurst and played bass in a punk band called Manufactured Romance.
A man has pleaded not guilty to the manslaughter of an off-duty prison officer early on Christmas Day.