Emergency services were called to Teville Gate, in Worthing, to reports a person had fallen from the car park at about 4pm.
A spokesman for Sussex Police said: “A male is in a serious condition and the air ambulance has landed to take him to hospital.”
Ambulance crews from SECAmb attended the scene to assist crews from the air ambulance service, according to a spokesman.
The spokesman added: “We responded to reports a person had fallen from height. The patient was assessed and treated for serious injuries before being airlifted to St George’s Hospital in Tooting.”
A spokesman for the Kent, Surrey and Sussex Air Ambulance (KSS) confirmed the air ambulance was called to an incident in Worthing and landed in Homefield Park, Worthing.