The California Highway Patrol issued the alert on behalf of the Hayward Police Department for Alameda, San Joaquin, Kern and Los Angeles counties.
The infant, Maxence Sirois, was last seen with her alleged abductor at about 1 a.m. Sunday near McBride Lane and Underwood Avenue in Hayward, the CHP said. Police identified the suspected abductor as 42-year-old Marina Kazakova.
Kazakova is believed to be driving a white 2016 Mazda CX-5 with California license plate 7SJW989.
The infant is described as about 2 feet tall, weighing 16 pounds, with blue eyes and no hair. Kazakova is described as 5 feet 6 inches tall, weighing about 128 pounds, with brown hair and brown eyes. She was last seen wearing a black shirt and blue jeans.
Anyone who sees the child, the suspect or the vehicle is urged to call 911 immediately, the CHP said.