Surveillance video captured the man, who appears to be in his 70s, inside the Goleta branch of the Bank of America around 6 p.m. Friday.
He threatened a teller with a gun, and gave her a note demanding money. He got an undisclosed amount of cash and walked out of the bank.
The FBI said he's the same robber responsible for a string of 13 holdups starting in August 2009.
A $20,000 reward is being offered for information leading to his arrest and conviction.