Police were called to the town's Braichlie Road and the Explosive Ordnance Disposal (EOD) unit called out.
Police Scotland later said it turned out to be a deactivated device from WW2 which had "no explosive capability" and was removed.
Insp Megan Heathershaw of Police Scotland said: "There was no threat to the public at any stage."
A building in Ballater was evacuated after an unexploded device was found.