Three other people from the other two vehicles have also sustained injuries, according to police.
The collision happened on the eastbound carriageway between junction 32 at Coryton Interchange and junction 30 at Cardiff Gate.
Both sides of the carriageway have been closed to traffic while emergency services attend.
The police tweeted: “M4 Eastbound closed from Coryton Junction 32 to Junction 30 following an incident. Please make alternative travel arrangements.”
Two ambulances and a specialist support service from Bridgend are at the scene after being called at 6:06pm.
Ambulances have been sent to the University Hospital of Wales, a spokesperson for the Welsh Ambulance Service said.
The spokesman could not confirm the number of people who were sent to hospital.
Traffic remains stationary, with the trapped eastbound traffic being sent back to J32.
Drivers stuck on the Westbound side is being diverted to the Gabafa interchange and the A470 back to M4 J32.
Some motorists have even abandoned their cars after the traffic ground to a halt this evening.
A police spokesman said: “South Wales Police can confirm that a serious road traffic collision occurred on the M4 close to junction 32 at Coryton.
“The incident, involving three vehicles, occurred at approximately 6pm. One man has sustained serious injuries.
“Three other occupants of two other vehicles involved in the collision were also injured.
“A full road closure is currently in place preventing access to the M4 at junction 30 and at junction 32. The closure is expected to be in place for some time.
“The public are thanked for their understanding and cooperation. “
Motorists have taken to social media after getting stuck on the queues.
Dale Ashford said: “M4 Eastbound Coryton, nastiest accident I’ve ever seen, motorway has been closed off and leave via junction 32.”
Peter Jones tweeted: “Just drove past on the other side on my way home – someone receiving cpr sadly – very nasty crash.”
Louise said: “Not long passed there westbound, there’s been a horrific accident. Saw someone receiving CPR and an air ambulance on the way. Awful.”
DJ Paul C added: “What is happening on the M4? Sat in traffic and about ten emergency service vehicles have gone past on the hardshoulder…”
Patric Morgan said: “#M4 eastbound closed at #Coryton. Really bad accident. Traffic looks like it’s being diverted down A470.”
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