A man armed with a shovel handle, entered the Centra in Old Bridge at around 7.30pm last evening.
He threatened a female staff member before making off with a substantial sum of cash.
The staff member was not injured but was left shaken by the incident.
Gardai later apprehended a man in his late 20's in the Old Bridge area.
He is currently being held in Clonmel Garda station.
The shop involved is owned Ely's, whose Cashel store was also targetted in a robbery last week.
