They backed the action by 397 votes to 223 after a 10-hour debate in the House of Commons.
Four Tornado jets took off from RAF Akrotiri, Cyprus, shortly after the vote.
A Ministry of Defence spokesman said the sorties had returned from the "first offensive operation over Syria and have conducted strikes".
Two of the four Tornados arrived back in Cyprus just over three hours after they left the base, landing shortly before 03:00 GMT.
BBC defence correspondent Jonathan Beale said the pair of Tornados had left RAF Akrotiri with three 500lb Paveway bombs each and returned to base without those weapons.
The Ministry of Defence is expected to give details of their targets later on Thursday, he added.
More about:
