Nancy Grace definitely made an impact on Monday night's Dancing With The Stars ... but it wasn't for her quick step. The CNN host had a wardrobe malfunction!

After her dance with partner Tristan MacManus, DWTS host Tom Bergeron noticed that a portion of Nancy's breast had popped out of her gown.

Bergeron said, "On the European version that would be perfectly fine."

Yikes! On with the show ...