The 16 inmates refused to return to their cells just after 9 a.m., and guards responded by locking up a section of the Hull prison to keep them isolated.
The maximum-security wing is in its own section of the Hull jail and other areas are not said to be affected.
Quebec provincial police spokesman Marc Tessier says no correctional officers have been injured or taken hostage.
Provincial police say their negotiators have been trying to determine the reason behind the protest.
Gatineau city police have also formed a perimeter around the building to ensure security.