Officers responded to 1333 Willow Pass Road shortly before 10:55 a.m. Tuesday on a report of a bank robbery, police said.
A preliminary investigation revealed that the man entered the bank, handed a note to a teller and demanded money before running out with an undisclosed amount of cash, according to police.
The man did not reveal a weapon and no injuries were reported, police said.
Officers tried to locate the man using a police K9 but he remains at large.
Witnesses described the suspect as a white man of medium build who is between 5 feet 8 inches and 6 feet tall. The man is believed to be in his 50s and was wearing dark clothing with his face partially covered at the time of the robbery, police said.
Anyone with information about the case is asked to call Detective Dave Ishikawa at (925) 603-5864. Those wishing to remain anonymous can call the Concord Police Department tip line at (925) 603-5836.