The teen is in hospital with a life-threatening condition after the attack on Tuesday (December 9) at 9.50pm.
He remains there at this time.
No arrests have been made but police are continuing to investigate.
A cordon has been in place all day today (December 19) at Clifton Rise, Fordham Park and Achilles Street.
A Metropolitan Police spokesperson said: “Around 21:50hrs on Tuesday, 9 November, officers attended Clifton Rise, New Cross, following reports of a stabbing.
“A 19-year-old man was treated at the scene for stab wounds. He was taken to hospital, where he remains in life-threatening condition.
“No arrests have been made, and police are making urgent enquiries.”
Anybody with information is urged to call 101, quoting CAD 7819/09DEC. Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.
