Police were called to Harrow on the Hill at 5.18pm on Wednesday, 9 November to reports of a stabbing.
Officers attended along with paramedics from London Ambulance Service (LAS). Three males were found with stab wounds.
They were treated at the scene by paramedics before being taken to the hospital. The condition of two of the males has been assessed as non life-threatening.
Another male was arrested at the scene on suspicion of assault. He has been taken into custody.
A crime scene has been put in place. Enquiries continue.
