No trains were stopping at Mornington Crescent station throughout rush hour due to the incident just outside its entrance in the early hours.
Police were called at 3.50am to Camden High Street and found a man in his 20s injured. He was taken to hospital and his condition was not believed to be life-threatening or life-changing on Tuesday morning.
Tube passengers heading back to work after the Easter weekend were advised to walk to Camden Town station instead, while nine bus routes were diverted away from Camden High Street.
However, there was still access to the high street for pedestrians.
The official Northern Line account posted on Twitter this morning: “Mornington Crescent station closed – On the request of the police. All trains are non stopping.”
Met Police added: “Police were called to Camden High Street at 3.50 to reports of a man injured.
“There have not been any arrests. Enquiries continue.”
The police cordon on Camden High Street began to be removed just before 10am and Mornington Crescent station reopened minutes later.