Before presenting Underwood with Entertainer of the Year, McConaughey told the audience how George Strait's boots once got him "lucky."
After collecting her trophy from him, Underwood was at a loss for words and blurted out: "I don't know what to say. I got nothin' ... I want to see those boots, Matthew."
Camila Alves - the mother of McConaughey's 8-month-old son Levi - was sitting in the audience.
Now, Underwood tells Fox News, "I'm so embarrassed, I totally embarrassed myself. I just blanked. You want to say something eloquent in a moment like that and I embarrassed myself."
"I'm sorry Matthew, I'm sorry to my family," she says. "I'm totally embarrassed."
Underwood wasn't too razzled: She still managed to mention her boyfriend, Ottawa Senators hockey player Mike Fisher, in her acceptance speech.
"Mike, baby, I wish you were here!" she said.