The drone plummeted into an exercise yard within Wheatfield Prison in west Dublin at around 10.00 GMT Tuesday.
A package containing suspected drugs was attached by a rope to the four-blade device but it got caught on wires designed to prevent airborne escapes by prisoners.
It's believed up to 20 inmates rushed to the device and managed to gather some of the contraband.
Prison guards noticed the commotion in the yard and intervened.
"We were alerted to an incident at Wheatfield prison yesterday morning," the Garda (police) press office told AFP.
"We were handed a device and an investigation is underway."