The robbery happened around 4:30pm Friday at Trustmark Bank, 6809 F.M. 1960 West in Houston.
According to investigators, the man entered the bank alone and handed a teller a threatening note, which demanded cash.
The teller gave him some cash, officials said, and the robber left the bank.
No one was physically hurt during the robbery.
The bank's surveillance cameras captured a photograph of the suspect during the robbery.
He is described as a white or Latino male in his 30s, 5 feet 8 inches to 5 feet 10 inches tall, 160-180 pounds with a wavy or curly dark brown hair.
He wore sunglasses, a blue T-shirt and jeans during the robbery.
Crime Stoppers is offering a reward of up to $5,000 for information leading to the charging and arrest of this alleged robber.
If you have information about this case, call the Crime Stoppers tip line at 713-222-TIPS or the Houston FBI office at 713-693-5000.