The incident is believed to have taken place between Chichester Watersports and The A285 turn off at about 8am today (Wednesday, May 18).
A large stretch of the road was closed temporarily and was reopened at 10.30am, police have said.
Minor injuries have been reported.
A spokesperson for Sussex Police said: “Minor-injury only collision involving three vehicles reported at 8.30am on May 18 on the A27 near Portfield Way, Chichester. Ambulance service also attended. Temporary road closures were in place until 10.30am.”
Footage from the scene shows a large number of police and ambulance vehicles as emergency services teamed up to help those involved in the collision and to clear the road.
Traffic is now clear and moving along the road.