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26 September 2014 Last updated at 10:49 BST
The strikes were expected as part of President Barack Obama's pledge to "destroy" IS, which has taken over large parts of Iraq and Syria.
IS is a radical militant group which has threatened to harm any non-muslims unless they convert to Islam.
They want to make a new country called the Islamic State.  It would join parts of Iraq and Syria together.
Obama has promised to try to stop the group and the US has already launched air strikes in Iraq since August.
But this is the first time the group has been targeted in Syria and is supported by some other Middle Eastern countries such as Jordan and Saudi Arabia.
Pentagon spokesman Rear Admiral John Kirby, said fighter and bomber jets and Tomahawk missiles were used in the attack.
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The US and its supporters including several Arab countries have launched the first air strikes against Islamic State (IS) in Syria, the Pentagon says.