Andrew McGrath, an inmate in custody at the Regional Psychiatric Centre in Saskatoon, died on Wednesday.
Correctional Services of Canada (CSC) said McGrath died of apparent natural causes following an illness. As in all cases involving the death of an inmate, CSC will be reviewing the circumstances of his death.
McGrath had been serving a life sentence for second-degree murder since Jan. 23, 1980.
His next of kin have been notified of his death.