Police were called to the incident on Streatham Green at 3.50pm on Monday (April 7).
The victim, a man in his 30s was taken to hospital with serious head injuries.
He remains in hospital in a critical condition.
Enquiries remain ongoing and a scene is in place.
If you have any information, contact police on 101 and quote CAD 4450/07APR25.
A spokesperson for the Metropolitan Police said: “Police were called at 15:50hrs on Monday, 7 April to Streatham High Road, SW16 following a serious assault.
“The victim, a man in his 30s was taken to hospital with serious head injuries where he remains in a critical condition.
“Enquiries remain ongoing and a scene is in place.
“If you have any information please contact 101 quoting CAD 4450/07APR25, or alternatively you can contact Crimestoppers anonymously on 0800 555 111, or via their website.”
