A woman, armed with a rock and wearing a mask, robbed the Scotiabank branch on Water Street in St. John's shortly before noon on Friday, according to the Royal Newfoundland Constabulary.
Police say the 21-year-old woman is in custody.
The RNC said the woman was stopped by bystanders until police could arrive on the scene and that all the money was recovered, when people picked it up and brought it back inside the bank.
Police said the investigation is ongoing.
The branch is closed and a sign posted on the door says it is because it has "just been involved in a robbery/emergency situation."