Police were called to a suspected robbery on Balham High Road at 23:34 last night where they found a man with stab injuries.
The 27-year-old was taken to hospital by Ambulance crews; his injuries are not believed to be life-threatening.
No arrests have been made and the crime scene remains in place while enquiries continue.
Anyone with any information is asked to call police on 101 on Crimestoppers to remain anonymous.