The patients were all at the Alberta Children's Hospital.
Officials are working to notify the individuals whose information was breached.
"I want to apologize to all patients whose privacy has been breached. AHS takes the privacy and confidentiality of patient information seriously, so I find this lapse intolerable,” AHS president Vickie Kaminski said in a written release.
The breaches were detected during audits of the two AHS databases, which revealed patient records were being inappropriately accessed by a staff member over a 14-month period.
The staff member no longer works for AHS.
Data that might have been accessed included patient history, contact information, date of birth, names of relatives and emergency contact information, AHS said.