The CoastHills Federal Credit Union in Atascadero was robbed around 4:05 p.m. Thursday, according to police scanner dispatches.
A white male in his early to mid-20s handed the teller a note saying he had a gun, though no firearm was visible.
He left the bank and got into a 2003 Mitsubishi Mirage or Lancer with a male driver.
The robber is described as 6 feet tall, 165 to 175 pounds with brown curly hair, a mustache and goatee. He was wearing a black and white baseball cap and a black T-shirt with a green and white design on it.
He was last seen heading south on San Luis Avenue in Atascadero.
This is the ninth bank robbery in SLO County so far this year.