Officers were called shortly after 8.50pm on Saturday, 13 March to Church Street, Croydon.
A 37-year-old man was found with gunshot wounds at the location, near to the junction with Reeves Corner.
He was treated at the scene before being taken to hospital where he remains in a critical condition.
Two men, aged 24 and 30, have been arrested on suspicion of attempted murder and are currently in custody at a south London police station.
Police are appealing for witnesses for the incident or anyone with information to contact police on 101, quoting CAD 7335/13MAR.
Detectives from the Specialist Crime South Command are investigating.