Police said a man with a gun came up to a woman making a deposit at the Wells Fargo on Hope Valley Road. The incident happened around noon.
The woman was carrying a deposit and was at the bank to complete a transaction for her employer.
Police are not sure how much money was stolen in Saturday's theft. The woman was not injured.
Saturday's mugging comes after a string of robberies at other banks in Durham that targeted women. Those crimes also happened during daylight and the victims were also carrying deposit bags.
Two men were charged in connection to April robberies.