Three men were seen to attack the two victims on West Green Road, Tottenham, at around 1.30pm on Friday, police said.
The assailants then ran off in the direction of Green Lanes and High Road, according to eyewitnesses.
Emergency services rushed to the scene where they treated the two men aged in their 20s.
One of the victims remains in hospital in a stable condition. The other managed to escape without injury, Scotland Yard said.
Detective Inspector Sal Minas, investigating, said: “This is a shocking attack that took place brazenly in the street, I am sure there would have been other witnesses to this act of violence.
“If you think what you saw might be insignificant, I urge you to contact us and report it. It could really assist the investigation.
“Bearing down on violence in London is our top priority and we will seek to apprehend those responsible.”
Four men have been arrested in connection with the incident. They have been bailed pending further enquiries.
Anyone with information is asked to contact police on 101 quoting CAD 3665/30OCT20.