The Entourage actor will appear in two episodes of the CBS drama, reports TVLine.
He will play Ryan, a patient at Seattle Grace with a cheery disposition, in a guest stint due to air on May 3 and 10.
Belfi's recent credits include roles on NCIS: Los Angeles, Castle and ABC's short-lived Charlie's Angels reboot.
He will also appear in a May episode of Fox's Bones titled 'The Suit on the Set'.
Switched at Birth star Vanessa Marano has also signed up to play a patient on Grey's Anatomy.
The series airs on Thursdays at 9/8c and will return to ABC on April 5. In the UK, Grey's Anatomy airs on Sky Living.
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Watch a promo for the next Grey's Anatomy below: