Police were called at around 12.30am on Wednesday, 22 August to reports of a stabbing in Avonley Road, SE14.
Officers attended and an 18-year-old male was taken to a south London hospital where his injuries were deemed not life-threatening.
There have been no arrests at this time.
Detectives from Lewisham CID are investigating the incident and would like to hear from anyone who either witnessed the stabbing, has footage of the incident, or has information that could assist the investigation.
Detective Chief Inspector Lesley Hamilton said: “At this early stage we believe the victim was attacked by three males who made off on foot towards New Cross Road.
“We understand there were many people in the area at the time of the incident and I am confident that there are people who witnessed the attack. I urge those witnesses to come forward. Any information provided will be treated in the strictest confidence.”
Anyone with information is asked to contact Lewisham CID by dialling 101 quoting CAD 184/22AUG.
Alternatively they can call Crimstoppers anonymously on 0800 555 111.