Elizabeth Wettlaufer has been returned to the maximum security Grand Valley Institution in Kitchener, Ont.
The former nurse was convicted in a series of deaths at nursing homes in London and Woodstock.
She had been transferred from Grand Valley to a psychiatric facility in Montreal to receive medical treatment.
Corrections Canada notified Susan Horvath, the daughter of one of Wettlaufer's victims by letter, indicating that she is now back in Kitchener.