South East Coast Ambulance Service said it sent four ambulance and two cars to the scene when it first received a called at around 3.15pm today (Wednesday April 10).
All five people have been taken to St Richard's Hospital including a man in his 70s, a man in his 20s, a woman and there is no further information available about the other two involved in the incident.
Four people were extracted from vehicles by fire crews who were sent from Chichester, Bognor, and one appliance sent from Hampshire Fire and Rescue Service.
A spokesman For West Sussex Fire and Rescue Service has released an updated statement in which a spokesman said: "We were called to an RTC involving three vehicles on the A27 westbound between Fishbourne and Stockbridge at 3.22pm this afternoon.
"Two engines were sent to the scene from Bognor and Chichester, along with an appliance from Hampshire FRS. On arrival, crews worked to extricate four people from the vehicles. They were successfully released using hydraulic rescue equipment and handed into the care of SECAmb.
"Crews remained at the scene to assist other emergency services, and we left at 4.32pm."