Zacharia, who joined the White House on Monday, has previously said she practiced law before entering politics and Trump had described her as a lawyer.
"You did not pass the bar exam, correct?" she was asked in an interview on Fox News' Hannity show.
"Correct," she said in response to the host, Sean Hannity.
"I did not," she said when Hannity asked if she ever took the bar exam a second time.
Zacharia earned her law degree from Pepperdine University in 2011, according to the university. Nearly all licensed US lawyers first obtain a law degree, but law school graduates cannot legally practice law in the US without first being admitted to a state bar.
On Tuesday during her first briefing, she took questions from just three reporters before ending the event in under 15 minutes. Her performance was criticised by some media commentators and political analysts, though Trump told reporters, "I thought she was very good."
When asked about her performance by Hannity, she said: "What I feel is I really stepped up to the plate to do the press conference, Sean, with very little prep time."
