Variety reported the 30-year-old professional dancer and 46-year-old actress will replace Mel B and Heidi Klum on the judges panel in Season 14.
Hough and Union join returning judges Simon Cowell and Howie Mandel. In addition, actor Terry Crews will replace Tyra Banks as host of the NBC reality competition in the new season.
NBC Entertainment alternative and reality group president Meredith Ahr confirmed the news in a statement to The Hollywood Reporter.
"One of the many secrets to the success and longevity of America's Got Talent is its fearless drive to reinvent itself," Ahr said. "The next evolution of the format brings in fresh expert eyes to join Simon and Howie on the panel."
"Gabrielle and Julianne are two of the most aspirational women in the business, on top of being electric entertainers with talent across disciplines," she lauded. "I am excited to see how their knowledge, compassion and sheer joy enhance the experience for acts and viewers alike."
Hough is a former competitor and judge on the ABC reality competition Dancing with the Stars, while Union plays Mary Jane Paul on the BET series Being Mary Jane. Crews hosts the AGT spinoff AGT: Champions and portrays Terry Jeffords on the NBC series Brooklyn Nine-Nine.
"It's officially official, I could not be more excited to announce I will be a judge on the upcoming season of @agt!!" Hough tweeted Monday. "The talent on this show is absolutely outstanding, and I have no doublt this next season is going to WOW. Thank you @nbc & my incredible team. Let's go!!!! #AGT."
Copyright 2019 United Press International, Inc. (UPI). Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.