The 27-year-old has moved to the Serie A outfit in a bid to earn more playing time, having only made 10 league appearances for I Rossoneri in the 2013/14 campaign.
"I want to repay that trust to the people at the club. I have spoken to Chievo coach Eugenio Corini and he has great confidence in me.
"He had followed me for a while and his words were crucial in my decision to come to Chievo. I am here now and ready to help this team do well."
Birsa signed for Milan last year from Genoa and is under contract with the San Siro side until June 2016.