Trout posted a video featuring several clips with his wife, Jessica, and family on social media.
"Baby Trout due August 2020," Trout wrote. "I don't even know where to begin. From seeing your heartbeat for the first time to seeing you dance around in mommy's belly.
"We are truly blessed and this is only the beginning! Little man, you have the best mommy already and I can't wait to be your dad! We are so humbled by this gift God has given us. We love you already, buddy!"
Trout's video featured his wife on the night before Thanksgiving, when she surprised her husband with the news after receiving positive results on pregnancy tests. The video also showed the couple breaking the news to other family members.
The Trouts married in 2017. They started dating while attending high school in Millville, N.J. Trout signed the largest contract in sports history in March 2019, inking a 12-year, $430 million contract with the Angels.
The Angels lost to the Chicago Cubs in a spring training game Monday at Sloan Park in Mesa, Ariz. They battle the Cleveland Indians at 3:05 p.m. EST Tuesday in Goodyear, Ariz. Trout, 28, won his third American League MVP award last season after hitting .291 with 45 home runs and 104 RBIs in 134 games. The eight-time All-Star has a .305 career batting average with 285 home runs in 1,199 games for the Angels.