The bicyclist was traveling north on Bancroft Road around 7:30 a.m. on Thursday when they were struck by a southbound Toyota SUV, police said.
The bicyclist sustained injuries and later died at a hospital. The driver of the Toyota was not injured.
The cause of the collision remains under investigation and no arrests have been made at this time.
Anyone with information on this collision should call Walnut Creek police at (925) 943-5844.