The suspect allegedly robbed the Bank of America branch at 2347 Telegraph Ave. at about 1:15 p.m. on April 23 and at about 12:10 p.m. Monday.
He allegedly handed the teller a note that indicated he had a gun and demanded cash before fleeing the bank, police said.
Bank of America is offering a $1,000 reward for information leading to the arrest and conviction of the suspect.
He is described as a black man in his 40s, standing between 5 feet 11 inches and 6 feet 2 inches with a medium build and scruffy beard.
Anyone with information regarding the case is asked to call Berkeley police at (510) 981-5742 or (510) 981-5900. To remain anonymous, call the Bay Area Crime Stoppers tip line at (800) 222-TIPS.