Armed officers made the arrests around 7.10pm yesterday in Whitechapel, Bayswater and Peckham.
Police said last night searches at six addresses were ongoing.
Scotland Yard said the men were being held under the Terrorism Act 2000 on suspicion of the commission, preparation or instigation of acts of terrorism.
The Metropolitan Police stated that the arrests were part of a “pre-planned, intelligence-led operation".
Two of the men were detained in Mansell Street, east London. A third man was arrested at a premises in Westbourne Grove, west London.
The fourth man was detained in Peckham Street, southeast London.
The men have been taken to a south London police station, and are continuing to conduct searches at six addresses.