The 30-year-old actress and 30-year-old model sported see-through floral looks at the 2016 Academy Awards, where Mara was nominated for Best Supporting Actress for Carol.
Mara turned heads in a Givenchy dress with cutout detail and also made headlines for her triple bun hairstyle. Teigen, who is pregnant with her first child by husband John Legend, showed off her baby bump in a Marchesa gown with burgundy embellishment.
Mara ended up losing to Alicia Vikander in The Danish Girl, while her Carol co-star, Cate Blanchett, lost Best Actress to Brie Larson in Room. Mara was previously nominated for Best Actress for The Girl with the Dragon Tattoo in 2012.
"They were both challenging for different reasons," she said of Carol and The Girl with the Dragon Tattoo to ABC News. "They're so different, both of them."
"It's nice to have someone as close to you as your sister who understands what it's like [to] live the life of an actor," she added of sister Rooney Mara, whose film The Martian was nominated for Best Picture.
Teigen attended the Oscars with Legend, who won an Academy Award for Best Original Song for "Glory" in 2015. The model appeared to make a face when Fox News contributor and Clueless actress Stacey Dash took the stage at the ceremony.
"I was making the face from the Stacey Dash moment ahhhhhhh not Sarah!" she explained on Twitter.
Quantico star Priyanka Chopra was among the other best-dressed actresses to wear sheer looks. Naomi Watts and Olivia Munn stunned on the red carpet with their respective beaus, Liev Schreiber and Aaron Rodgers.