The first deliveries are scheduled for the second half of 2012 and the contract includes options for five additional Superjet 100 jets, which seat 98 passengers.
Superjet is a joint venture between Finmeccanica's Alenia Aeronautica and Russia's Sukhoi.
The upstart airline has been expanding in recent months to take advantage of the demise of rival airline Mexicana, which stopped flying in August amid deep financial troubles.
Interjet's chief executive Miguel Aleman Magnani said in December the company was considering selling a stake to a foreign partner or listing its shares on the local stock market to boost growth.
It currently operates 22 A320 Airbus jets and is scheduled to receive four more A320s this year.
Interjet has 20 percent of the domestic market, behind leader AeroMexico and ahead of Volaris, which it tried to take over for USD$360 million in 2010.