Four fire crews were called to the scene and one of the drivers had to be cut from their car.
The West Midlands Ambulance Service spokesman added: “Crews arrived to find a car that is believed to have mistakenly joined the motorway the wrong way and subsequently been in a serious collision with two other vehicles.
“The car believed to be travelling the wrong way, driven by an elderly gentleman, came to rest up a grass embankment following the crash.
“The man had suffered a small head laceration, further minor injuries and was shaken up. He was treated at the scene by medics and with the doors of the vehicle unable to be opened was released by the Fire Service.
“Once out, the man received further treatment by ambulance crews and due to the mechanism of the crash was transferred to University Hospital Coventry and Warwickshire for further checks.
“The occupants of two further vehicles involved in the crash, a man in his 40s and a man in his 50s, were both checked over by ambulance crews but were uninjured and discharged.
“Considering the circumstances of the crash and the damage to the vehicles, the three men are extremely lucky not to have suffered more serious injuries.”
A spokesman for Warwickshire Fire and Rescue Service said of the incident: “Four fire crews are currently at the scene of a four vehicle road traffic collision located on the southbound carriageway of the M40 between junction 16 Henley in Arden and junction 15 Longbridge island, Warwick.
“The ambulance service and police are also in attendance. There are several casualties being treated by the ambulance service and one casualty requires cutting from a car by fire crews using specialist cutting equipment.”