The arrest at a shop in south London was planned and followed by a joint investigation by Scotland Yard's terrorism command and MI5, UK's domestic counter-intelligence and security agency.
The Metropolitan Police detectives are investigating if the man had been influenced by the Islamic State (ISIS) terror group as part of their inquiries.
"He was taken to a central London police station and remains in custody at this time. Officers are searching a residential address in south London. Enquiries continue," police said.
Arrests under the UK's terrorism legislation mean an individual has come under suspicion, but that may prove unfounded.
Also Read
Of 289 people arrested on suspicion of terrorism-related offences last year, 102 were charged, according to figures from the Royal United Services Institute prepared for 'Sky News'.
The fear of a terrorist attack being carried out by people with connections to or inspired by ISIS led the Joint Terrorism Analysis Centre to recommend raising the threat level in August last year to severe, its second highest level.