Charges have been laid against a man already serving time at Millhaven Institution for the alleged assault of another inmate with a weapon.
An inmate was rushed to hospital after the attack at the maximum-security federal institution on Friday.
Police say the victim was left seriously injured after being attacked with an edged weapon but is recovering in hospital.
Correctional Service Canada (CSC) says no staff or other inmates were injured.
The OPP‘s penitentiary squad was called in to help with the investigation.
Inmate Ekene Angibo, 24, has been charged with aggravated assault, assault with a weapon, possession of a weapon for a dangerous purpose, and carrying a concealed weapon.
The accused remains in CSC custody and was scheduled to appear in Napanee court on Friday.
The Correctional Service of Canada says it is reviewing the incident.