Spokeswoman Shannon Oickle of Springhill Institution says John Leonard MacKean, 65, died of natural causes on Wednesday.
MacKean began serving a two-year sentence on June 24 for sexual assault and for communicating for the purpose of obtaining sexual services from a person under 18.
The Correctional Service of Canada says it will review the circumstances of his death, which has been reported to the police and the coroner. The Correctional Service says in a news release that all cases involving the deaths of inmates are the subject of a review and notification is always given to the police and the coroner.
MacKean was sentenced for sexually assaulting a 16-year-old boy, who testified he was blindfolded and chained to a bed during the ordeal.
The Halifax man was also sentenced to three years' probation.
Another man accused in the case was sentenced last year to 11 years in prison. David James LeBlanc pleaded guilty to kidnapping, forcible confinement, sexual assault, uttering threats and breach of conditions.
In court, Crown attorney Lloyd Tancock said MacKean did nothing to assist the frightened young man who testified he was held for eight days at the cabin in Upper Chelsea, about 130 kilometres southwest of Halifax.
It was obvious from the boy's appearance that he was underage, he said.
The boy told the court MacKean performed oral sex on him on Sept. 20, 2012, and that he'd been able to identify the man with his limited view beneath the blindfold as a balding, heavy-set man who wore glasses.
MacKean has admitted he had a sexual encounter, but denied in court that he knew the boy's age. He said he would have helped the youth if he'd seen signs of distress.
LeBlanc was arrested in northern Ontario in September 2012 after a Canada-wide manhunt.
At the time, police were also searching for Wayne Alan Cunningham, 31, whose body was later found near the area where LeBlanc was arrested. Foul play was not suspected in his death.
An agreed statement of facts in LeBlanc's case said he offered the teen a painting job and drove him in a van from Halifax to Lunenburg County on the pretext of picking up supplies.
The youth later escaped and a woman reported seeing a barefoot teenager at her doorstep, chained at his wrists and ankles.