Kathryn, 28, accessorised her red gown and its thigh-high leg slit with a bold red lip, and the support of Peter, 66, who walked the red carpet with her in a classic black tuxedo.
The You star was nominated for best-featured actress in a musical for her performance as Bella Fox in Jagged Little Pill.
Peter, known for his role as Sandy Cohen in The O.C., was also previously nominated for best-featured actor in a play in 1986, after his performance as Edmund Tyrone in Long Day’s Journey Into Night.
Kathryn celebrated her nomination in October on Instagram.
“For the last three years I’ve had the pleasure of working alongside the finest artists I could have ever dreamed of making a show with and that in and of itself has felt like winning the lottery,” she wrote.
“This is a very cool feeling I didn’t think I would ever feel and I’m just really grateful you all wanted to see our play and I can’t wait until Broadway is back at it,” Kathryn said, before concluding with a sweet nod to her father, “Going to call my dad back now.”
Although Jagged Little Pill led the nominees with 15 nods, Kathryn, who was nominated alongside co-stars Celia Rose Gooding and Lauren Patten in the same category, did not win the award.
Patten won best-featured actress in a musical, ahead of Robyn Hurder for Moulin Rouge! The Musical and Myra Lucretia Taylor for Tina — The Tina Turner Musical.
Alongside Patten and Gooding, Kathryn later performed onstage at the ceremony with the wider Jagged Little Pill cast.
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