Four Tornados took off from RAF Akrotiri in Cyprus shortly after British MPs voted to approve bombing, the BBC wrote.
The strikes focused on six targets in an oil field under IS control in eastern Syria, the BBC understands.
On Wednesday, MPs voted by 397 votes to 223 for UK action in Syria after a 10-hour Commons debate.
Two of the four jets have now returned to base. The Ministry of Defence confirmed they had carried out the "first offensive operation in Syria".
BBC defence correspondent Jonathan Beale said the first pair of Tornados had left RAF Akrotiri with three 500lb Paveway bombs each.
They returned to base shortly before 03:00 GMT without those weapons, he said.
The jets used their Raptor pods - special long-range photography equipment - for surveillance, before dropping the Paveway bombs, our correspondent understands.
An RAF Reaper unmanned drone was also in the air to provide intelligence, he added.