The 32-year-old is now being questioned at a central London police station.
Police said the arrest was not linked to that of another man, aged 30, in Somerset, also by officers from the Met's Counter Terrorism Command.
That individual - a member of the armed forces - is being held on suspicion of Northern Ireland-related terrorism.
The 32-year-old was detained on Wednesday morning under Section 5 of The Terrorism Act 2006.
A man has been arrested in north-west London on suspicion of preparing terrorist acts linked to Syria, the Metropolitan Police have said.