The film revolves around eight college friends who reunite for a wedding. The cast will also feature Anna Paquin, Josh Duhamel, Malin Akerman, Elijah Wood, Adam Brody and Jeremy Strong.
Katie will play Laura, the maid of honor to Anna Paquin's Lila, the bride. Laura and Lila are best friends who both have a past with the groom, played by Duhamel.
Katie will also be executive-producing the film, which begins shooting this week in New York City.