The former first-rounders both went yard in Kansas City's 12-11 loss to Texas in Cactus League action Monday.
Moustakas, the second overall pick in 2007, slugged a three-run homer and drew a walk. Hosmer, selected third in the 2008 Draft, was 2-for-2 with a solo blast and scored twice.
Moustakas, who entered the game as a pinch-hitter in the sixth inning, tied for the Minor League lead with 36 homers in 2010. The 22-year-old also drove in a career-high 124 runs and batted a personal best .322 for for Double-A Northwest Arkansas and Triple-A Omaha.
"It's always fun to hit a home run, especially in my first time in big league camp, but hopefully there will be some more," Moustakas told MLB.com. "I remember saying, 'Don't act like it's your first one.' So, hopefully, it's not my last."
Hosmer was promoted to the Naturals shortly after Moustakas' departure, and he went deep 13 times in 50 games in the Texas League. Both were recently named to MLB.com's Top 50 Prospect list, with Moustakas checking in at No. 7 and Hosmer at No. 8.
Moustakas is vying for a spot on the Royals' Opening Day roster, competing with veteran Pedro Feliz at third base. Hosmer, who turned 21 during the offseason, is likely ticketed to be the starting first baseman for Triple-A Omaha.
Rangers prospect Jurickson Profar, who made his pro debut in 2010 with Spokane, drove in a run with a seventh-inning double that proved to be the difference in the game. Profar entered the game in the fifth, taking over for Elvis Andrus at shortstop.
Chris Dwyer, a fourth-round pick by the Royals in 2009, took the loss, allowing three runs on two hits in an inning of relief. Will Smith, who was 5-3 for Royals affiliates after being acquired on July 22 from Los Angeles, tossed a perfect inning.
Former first-rounders Aaron Crow and Mike Montgomery are slated to pitch for Kansas City on Tuesday against San Diego.