Oxford Circus station was evacuated and closed while emergency service dealt with a "casualty on the track".
Police were called to the station at 12.36pm and found a person with potentially life-threatening injuries at the scene.
The incident is not being treated as suspicious, police said.
The Victoria line was initially suspended while police, paramedics and firefighters remain at the station.
Once services resumed, there was severe delays on the rest of the line. The station reopened at around 2pm.
An earlier statement from TfL said: "No Victoria line service while emergency services deal with a casualty on the track.
"London Underground tickets will be accepted on Southeastern trains and local bus services via any reasonable route."
Pictures from the scene show a huge emergency services presence as the station was cordoned off.
