British Transport Police were called at 3.49pm to the tube station. One person was taken to hospital but their injuries are not life-threatening. There are currently no trains stopping at the south London station.
A Spokesman for British Transport Police said : “Police were called at 3.49pm to Clapham South station following a report of stabbing.
“A victim has been taken to hospital with injuries that are not believed to be life-threatening. Officers are currently at the scene and the station has been closed temporarily while they carry out enquiries.
The Northern Line official Twitter account said: “Clapham South station is closed, while the police carry out an investigation.”