Goodwin says that's not unusual for her.
"Last year to the Vogue's Met gala, I wore a Top Shop dress," she said in an interview Thursday.
Goodwin, who's also known for her roles in the film "Something Borrowed" and HBO's "Big Love," said she loves high luxury design but doesn't let a price tag determine what she buys.
"My day-to-day wardrobe I do mix it up," she said. "I'll wear something from Target along with something by YSL. It's about finding the right items that make you happy."
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"I thought it was incredibly glamorous and appropriate for the occasion, conservative enough for the occasion," she said.
She said she gets excited when she finds clothes she likes that are "affordable and accessible to the public."
Noting that H&M made 999 other copies of the dress she wore, she said she hopes "they get snatched up immediately by ladies who think that high fashion is beyond their grasp because it's not."
Goodwin said she dresses "selfishly" and is conscious of what she wears because that is how she defines and expresses herself.
"I think of clothes a lot like costumes," she said. "I think of what I wear in real life as being my real life character's costume."
Her affinity for costumes had a role in her taking on her new "Once Upon a Time" gig. She plays Snow White and alter ego Mary Margaret in the ABC fairytale drama, which has its season finale Sunday at 8 p.m. Eastern.
She said the job involves lots of wardrobe changes.
"The costumes are insane on 'Once Upon a Time,'" she said. "It did influence my taking the job, the fact that not only would I be horseback riding and sword fighting and traipsing through the woods but I would be doing all those things in insane, medieval garb."
She said she knew it was a perfect fit as soon as the show's costume designer told her he was going for "a couture fairytale."
Associated Press writer Alicia Rancilio contributed to this report.