Whitney Leavitt is making a major leap — going from reality TV to the Broadway stage — and her costar Mark Ballas is loving every second of it!

We caught up with Mark in NYC Thursday, and he couldn’t stop hyping Whitney’s turn as Roxie Hart in “Chicago” — saying she’s absolutely crushing it.

Catch the full clip … ’cause when we asked if she should go full-time Broadway, he definitely had thoughts.

As for Whitney, she doesn’t seem opposed to making the switch … especially after admitting she’s still figuring out her future on “The Secret Lives of Mormon Wives.”