The world's biggest restaurant chain will also sponsor Justin's 35-country world tour, but have refused to say how much they are paying him.
A spokesman for McDonald's just said, "We are spending a great deal."
In the spotlight
Justin, who's just been named the world's sexiest man, has been in the media spotlight recently.
As well as winning three MTV Video Music Awards, he's been dating Charlie's Angel's star Cameron Diaz.
McDonald's hopes that his face and voice can sell burgers around the globe.
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Justin Timberlake interview
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