A farmer reported that the shotgun, a single-barrelled model, was taken from the rear footwell of his truck on his farm some time between lunchtime on Thursday and 11.20am on Friday.
The shotgun was licensed, there was no ammunition in the vehicle and it wasn't loaded.
Staffordshire Police has not confirmed where on the border the incident took place, but urged residents to take care of their registered firearms.
DC Martin Smith, of the Southern CID team, said: "We urge everyone to always take care of any licensed firearms they own.
“You should always keep what can be dangerous weapons locked somewhere secure and where you know they are safe.
“Incidents like this will always cause concern but we are searching for the shotgun that was taken and will do everything we can to keep our communities safe.”