Fraser Mooney, spokesman for South West Health, says the employee of the Roseway Hospital in Shelburne gained access to 707 patient records.
Mooney says the breach was discovered in mid-April after another employee notified a manager.
Mooney says the employee was placed on leave as an audit was conducted to determine which files were opened without authorization.
He says the employee, who worked at the hospital for about two years, has since been fired.
Mooney says the employee did not have access to detailed information like medical charts.