The boys, ages 12 and 13, were crossing Cloverdale Boulevard by South Street in a marked crosswalk at 6:55 p.m. when they were hit by the car, driven by a 75-year-old man.
One boy was taken by ambulance to Healdsburg Hospital and the other was taken to Oakland Children's Hospital by helicopter. The boys remain in serious condition.
The 75-year-old driver was not injured and cooperated with the investigation. He is not believed to have been drinking, speeding or using his cellphone, police said.
Anyone who witnessed the collision has been asked to call Officer John Camara at (707) 894-2150.