Among them Casino Woodbine, Casino Ajax and the Great Blue Heron, all owned by Great Canadian Gaming Corp.
The casino's are opening their doors despite indoor gathering limits of no more than 50 people.
Table games and other amenities will remain closed, only slots will be open to gamblers.
Patrons have to make a reservation in advance and are allowed a two hour play session.
The next available reservation at Woodbine is October 2nd.
The two casinos in Niagara Falls remain shuttered.
A note on the website for the two, says management is currently reviewing the reopening requirements and capacity restrictions.