Theresa Cannon, 32, of Wilmington, was arrested for the robbery at Louviers Federal Credit Union at 2162 Kirkwood Highway in Newark on Wednesday afternoon.
Police say Cannon walked into the bank, wearing a baseball cap down over her face, at 4:01 p.m. and gave a demand note to a teller.
The teller handed over an undisclosed amount of cash, and the suspect fled on foot.
Troopers responding to the scene say they spotted Cannon walking on Kirkwood Highway and arrested her after a short foot pursuit.
Cannon was charged with robbery and wearing a disguise during the commission of a felony.
She is being held on $10,000 secured bail.