A remote-controlled flying object managed to fly over the exterior wall of the Hull jail and over the outdoor courtyard on Sunday morning.
It happened just after 11 a.m. Sunday, according to Stephane Lemaire, president of the union governing Quebec's correctional employees.
Officials don't know if the orange object dropped anything into the courtyard or not, and the drone itself was not recovered.
There are no suspects and no arrests have been made.
Lemaire said he wants correctional staff equipped with the tools to disable such drones.
Meanwhile, correctional staff are performing two patrols of the perimeter daily instead of one with staff who have the power to make arrests.
An official with the jail had earlier said inmates were in the yard when the drone flew over, but later issued a correction and said no inmates were in the yard.
Quebec's ministry of correctional services has not responded to Radio-Canada requests for comment.