The arrest was made in Hayle last night under 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, the BBC reported.
The man, who was arrested at the Balti King restaurant in Fore Street, is being questioned at a station in the Devon and Cornwall force area.
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The arrest "was not made in response to any immediate threat to public safety in Hayle", he said.
Hayle is a small town in west Cornwall, England.
"Our officers will continue to maintain a presence in the area, offering reassurance to the local community," he said.
British counter-terrorism police have made a number of arrests linked to the conflict in Syria in recent weeks, including in Bedfordshire, Hampshire and London.
Sectu would not confirm whether the Hayle arrest was linked to any other cases.