The singer popped into the Peter Som runway show on Friday during New York Fashion Week wearing a summery pale pink dress — actually by designer Ted Baker.
Underwood said she loves fashion shows, but doesn't get a lot of time to attend them. "I just thought I'd come in for the day and go along for the ride," she said.
On the runway, Som showed an appealing mix of smartly tailored coats and interesting graphics on dresses short and long.
The most interesting print: a pretty blurred floral that could make you feel a little dizzy.
"I love florals," Som said. "These are all roses. I was trying to give things a bit of mystery."
Also attractive were Som's tailored short coats. He said they were inspired by looking at photos of "Jane Birkin and her peacoats." Birkin, an English actress and singer, first became known for her free-spirited style in the 1960s.
As for Underwood, she said she is writing for a new album. She doesn't have any immediate plans to do another televised musical like "The Sound of Music," which she starred in last year.
"I'm excited to get back to the things that I know!" she said.
Underwood later popped up at Rebecca Minkoff's runway show.