"We decided to announce that we're having another boy," Cavallari, 27, said on Instagram Saturday.
Cavallari and Cutler, a Chicago Bears quarterback, found out the sex of the baby during the holidays, People reported.
The couple have a 17-month-old son, Camden Jack.
"Of course I want a little girl, but another boy would be a ton of fun too, so I really don't care either way," she said in November. "There's great things about both."