A road traffic collision took place on the B4038 Rugby Road, Kilsby on Sunday.
A green Vauxhall Astra was driving along the road at about 2.15pm when it was involved in a collision with a red Ford Fusion.
The 29-year-old woman driving the Astra and a six-year-old boy passenger were taken to Queens Medical Centre in Nottingham by air ambulance. A one-year-old boy who was also in the Astra was taken to Queens Medical Centre by land ambulance.
The 49-year-old man who was driving the Fusion was taken to University Hospital Coventry by land ambulance.
All four people sustained serious but not life threatening injuries.
Police would like to speak to anyone who may have witnessed this incident or have information regarding it.
Witnesses or anyone with information is asked to call the Drivewatch Hotline on 0800 174615.