The employee, 43, was arrested Friday night by Quebec's provincial police following a search inside the St-Jérôme detention centre. An inmate, 44, was also arrested.
Sources have told the CBC's French-language service, Radio-Canada, that the jail employee was helping the inmate obtain drugs. The pair were allegedly in a romantic relationship.
The employee faces charges of drug trafficking.
The inmate faces charges of conspiracy and possession of narcotics.