Two Royal Air Force (RAF) Tornados based in Cyprus fired four Brimstone missiles on two IS vehicles, including an armed pick-up truck, the ministry said in a statement.
"Two Tornado GR4s from RAF Akrotiri conducted an armed reconnaissance mission in support of Iraqi government forces west of Baghdad," it said.
"They were tasked to examine a location suspected of being used as an ISIL command and control position.
"At the scene they were able to identify ISIL activity and two vehicles, one of which was an armed pick up truck.
"Four Brimstone missiles were used to conduct a precision attack on the vehicles. Initial analysis indicates that the strikes were successful."
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British MPs last week approved a motion to join in a US-led military campaign against IS jihadists operating in Iraq.
The RAF conducted their first strikes on Tuesday, bombing an artillery post and an armed truck used by the IS militants.
It did not say where, but said the strikes aided Kurdish troops in the area.
Work and Pensions Secretary Iain Duncan Smith on Tuesday revealed that both coalition government partners were also in favour of action against IS fighters in Syria, but that it was blocked by the opposition Labour party.