The incident happened in Brook Street near Oxford Street at around 3.30am today (December 30).
Officers and London Ambulance Service attended and found a man who had been stabbed.
He was taken to hospital for treatment where his condition was assessed as life threatening.
Just before 5.40am, a vehicle was stopped in Eltham in connection to the incident.
The occupants, two women aged 34 and 39, were arrested on suspicion of attempted murder.
The 39-year-old woman was also arrested on suspicion of driving whilst unfit through drugs and possession of a Class B drug, namely cannabis.
A crime scene remains in place while the investigation is ongoing.
A spokesperson for Metropolitan Police said: “On Monday, 30 December at around 03:30hrs, officers were called to Brook Street, W1, following reports of a stabbing.
“Officers attended the scene alongside the London Ambulance Service. A 36-year-old man was taken to hospital by ambulance where his condition has been assessed as life threatening.
“At 05:49hrs, a vehicle was stopped in Eltham in relation to this incident. The occupants, two women aged 34 and 39, were arrested on suspicion of attempted murder.
“The 39-year-old woman was also arrested on suspicion of driving whilst unfit through drugs and possession of a Class B drug, namely cannabis.
“A crime scene remains in place while the investigation is ongoing.
“Anyone with information should call police on 101, providing the reference 802/30DEC.
“Information can also be provided to Crimestoppers, anonymously, by calling 0800 555 111.”