The 27-year-old has moved to the Verona outfit in a bid to earn more playing time having only made 10 league appearances for the Rossoneri in the 2013-14 campaign.
"I am very happy to have moved to Chievo," Birsa told Chievo TV. "I arrive here having had a good first half of the season at Milan and looking to give my very best.
"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 summer from Genoa and is under contract with the San Siro outfit until June 2016.