The incident happened at 7.50am near the junction with Amesbury Avenue, and Streatham Hill remains closed as police investigate.
Despite the arrival of the air ambulance and paramedics the man later died.
A police spokesperson said: “It is believed a car has collided with three other vehicles, including a lorry and a bus route number 109.
“It is not clear whether the death of the man is a direct result of the RTC.”
There have been no arrests in connection with the incident.