Police say the 4-year-old was sitting in the rear passenger seat and was shot in the head.
He was taken to a children's hospital for surgery.
The Cleveland, Ohio, child, who has not yet been identified, was traveling with his mother in an SUV on the I-90 near the Dead Man's Curve on Sunday night.
Miraculously, officials said the bullet did not enter the boy's brain.
The woman at the time was driving her 4-year-old son and her 7-year-old daughter. She pulled off on the East 55th exit and the boy was taken to the hospital.
The mother told officers the vehicle started following her onto Interstate 90 about midnight, police said. Cleveland CMS rushed the child to the University Hospitals Rainbow Babies and Children's Hospital.
However, no arrests had been made as of Monday afternoon.
Anybody with information is bring asked to call investigators at 216-621-1234.