The 26-year-old was arrested in Hayle on Monday night under section five of the Terrorism Act, Devon and Cornwall Police said.
Officers from the South East Counter Terrorism Unit (Sectu) – which is led by Thames Valley Police – were also involved in the pre-planned arrest.
Sectu confirmed the arrest was related to the ongoing conflict in Syria.
This must be the most exciting thing to have happened in Cornwall since Manderley burnt down.