Terick R. Goodwin, 39, Bridgeport, Conn., was arrested by Watertown police Wednesday morning with failing to register as a sex offender.
Police said Mr. Goodwin told law enforcement last July that he was living at 136 William St., but he was not actually living there.
He was sent to the Metro-Jefferson Public Safety Building, where he was to be arraigned Thursday morning.
Mr. Goodwin is a Level 1 sex offender, police said. According to state law, a Level 1 sex offender does not have to be listed on the state sex offender registry website.
It was unclear on Wednesday what crime he committed to become a Level 1 sex offender.