Police and paramedics scrambled to South Ruislip station after receiving reports of a stabbing at around 4.25pm.
South Ruislip station was closed after police were called to the scene, with no Central line or Chiltern Railway trains stopping at the station.
A police spokesman added: "Officers were called to South Ruislip Underground station at 4.24pm tonight following reports of an assault at the station.
"Paramedics also attended and a young man has been taken to hospital. His injuries are not believed to be life-threatening at this time."
There are also unconfirmed reports that a second teenager suffered stab injuries to his leg.
Speaking to the Standard, local resident Richard Culham said he came out of the newsagent to see a "teenager in a grey tracksuit that had been stabbed in the leg".
He added: "I got some serviettes from the takeaway shop for him, when I went to walk home I saw a crowd gathering under the railway bridge.
"I went over and saw a boy in school uniform lying face down on the pavement. Apparently, he had been stabbed in the side or stomach, all I could see was his body shaking like he was in shock."
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