Emergency services rushed to the junction of the High Street with Bedford Road around 9pm last night (April 10).
A man was found injured and treated at the scene by paramedics before being taken to hospital “as a priority”.
His condition is not known at this stage, nor if there have been any arrests.
Clapham High Street is still closed after 12 hours by a police cordon under the railway bridge, near Clapham North Underground and Clapham High Street Overground stations.
The train stations remain open, but Clapham High Street is closed southbound between Bedford Road and Aristotle Road.
The Metropolitan Police has also been contacted for comment on the incident.
A spokesperson for London Ambulance Service said: “We were called at 9.09pm on Thursday 10 April to reports of a stabbing at the junction of Clapham High Street and Bedford Road, SW4.
“We sent resources to the scene, including ambulance crews, a paramedic in a fast response car and an incident response officer. We also dispatched a trauma team in a car from London’s Air Ambulance.
“Our first paramedic arrived in four minutes.
“We treated a man at the scene and took him to a major trauma centre as a priority.”
