Trout posted the message Thursday on the social media platform. The two-time MVP and seven-time All-Star is currently hitting .366 with five home runs and 12 RBIs, while leading the league with 17 walks and a .571 on-base percentage.
"Dear Mike Trout," the letter said. "When you play at the game, I'll have front row seats! And you'll maybe see me! I'll be right in front of home plate. I drew you a picture. I hope you like it! I hope you can write me back!"
The girl, named Anne, also asked Trout to sign her hat. She drew a picture of herself standing alongside the Angels star.
"Thank you Anne!," Trout wrote for the caption on the post, which had nearly 100,000 likes by Friday morning.
Trout went 1-for-5 with a run scored in the Angels' 11-10 loss to the Seattle Mariners on Thursday at Angel Stadium in Anaheim, Calif. He has one hit in three consecutive games.
The Angels host the Mariners in the second game of the series at 10:07 p.m. Friday in Anaheim.