Two teenagers were arrested and a knife recovered at the scene as dozens of police surrounded the entrance to the station.
The air ambulance landed in Iceland car park with eyewitnesses reporting seeing a victim being stretchered off in to an ambulance.
Brigstock Road was cordoned off and it could clearly be seen that paramedics had worked on the victim near to the entrance in to the station.
There were at least 30 plus officers in and around the station.
A British Transport Police spokesperson said: “Officers were called to Thornton Heath station at 7.43pm last night (8 May) following a report of a stabbing.
“Paramedics also attended and a 15-year-old boy was taken to hospital for treatment where he remains. His injuries are not believed to be life threatening.
“Two young men, aged 16 and 18, were arrested at the scene in connection and taken to police custody for questioning. A knife was also recovered from the scene by officers. Enquiries into the incident are ongoing.”
The Chronicle also witnessed a number of officers on Liverpool Road last night which was also briefly cordoned off with a dog unit searching the street.
This latest stabbing happened as Sadiq Khan claimed victory in the mayoral election despite violent crime rising in the capital.
A London Ambulance Service spokesperson said: “We were called at 7:22pm tonight (8 May) to Thornton Heath railway station to reports of a person injured.
“We sent a number of resources to the scene: an incident response officer, an advanced paramedic practitioner, a clinical team manager, a medic in a response car and an ambulance crew. We also dispatched London’s Air Ambulance.
“We treated a male at the scene and took him to a major trauma centre by road.”