The center fielder made the announcement on Twitter Monday night.
"Little man, you have the best mommy already and I can't wait to be your dad!" Trout posted on Twitter.
Trout married longtime girlfriend Jessica Cox in 2017. Baby Trout is due this August.
The 28-year-old Trout is widely considered one of the best players in the game, with three AL MVP awards and eight All-Star selections.
Last year he signed a 12-year $430 million deal with the Angels, the biggest contract in the history of American sports.
This weekend, Trout also showed off his athletic versatility.
Video shows him making a monster swing at a golf driving range in Scottsdale, Ariz. where the team is holding spring training. His teammates laughed and cheered after the ball sailed off deep into the night sky.