The Northern Line has been suspended between Golders Green and Edgware due to a person under a train at Burnt Oak.
British Transport Police were called to the station in Watling Avenue at 2.23pm and said the man survived the incident.
Services remain suspended while the incident is fully investigated but a spokesman said it is not being treated as suspicious.
Transport for London says bus routes 114, 251, 302 and 305 are subject to diversion and delays in Watling Avenue because of the incident.
There are also minor delays on the Northern Line between Camden Town and Golders Green.