One calf was born June 7 and the second was born June 22 weighing in at 19 pounds.
The addax antelope, native to Africa's Sahara deserts, is on the brink of extinction, with only 300 living in the wild, WLS-TV, Chicago reported.
Nearly 200 of the animals live in 19 accredited North American zoos.
The Brookfield Zoo had its first addax birth in 1941 and has since contributed 141 calves to the North American population of the animal.
The addax antelope is known for its adaptation to live in drier, desert climates. Its hooves are wide and large, allowing it to walk on top of loose sand. Its legs are shorter than most antelope to help steady it on shifting sands.
The animal can go nearly its entire life without drinking water, deriving moisture instead from sap of vegetation and dew.