Officers are investigating allegations of "non-recent sexual offences" at St Margaret's Church in Warnham.
Detectives say they are looking into allegations that a male member of the choir, then aged between nine and eleven, was sexually assaulted by an adult in the church and elsewhere on several occasions between 1981 and 1983.
Police believe that further offences may have been committed against other boys during the same period.
In a statement Sussex Police confirmed a 55-year old man now living in Walton-on-the Naze, Essex, was arrested on suspicion of the sexual assaults.
He's been released on bail.
Detective Superintendent Jason Tingley said: "If you have any information that would assist our investigation, including information about any other offences, please contact us via 101, quoting Operation Barnwood, and arrange to talk in confidence to experienced detectives"
The Diocese of Chichester said it was working closely with the police on the investigation.
A spokesperson for the Diocese said today: "We are cooperating fully with this investigation by Sussex Police and hope that anyone with relevant information will come forward and contact the police."
A statement urged anyone requiring support to contact the Diocese's safeguarding team on 07468 698990.
