The two infielders from Chatsworth High in Northridge, Calif., went out to a steakhouse for dinner after the Royals beat Houston 4-2 in the opener of a three-game series.
A friend of Moustakas' father-in-law runs the restaurant and kept it open late for the ballplayers.
It was the first time the two had seen each other since Moustakas' wedding Jan. 4. Dominguez was a groomsman in the wedding.
"We had some good arms and good glove men in that wedding," joked Moustakas. "It was a pretty good group of baseball players walking down the aisle.
Moustakas married his high school girlfriend, Stephanie.
"Matt knew her when we were growing in the Valley and we hung out a bunch together," Moustakas said. "It was cool to be able to have him there with us."
Both players have been struggling at bat this season. Moustakas went 0-for-4 in the game and is hitting just .100. Dominguez, who had one hit in four at-bats, raised his average to .195.
"We talk a little bit about baseball, but mainly from being friends back in the day," said the 25-year-old Moustakas.
They text each other occasionally.
"We're not too good with our phones, so we're not much on the communication," Moustakas said. "If I see he had a good game, I'll text him."
The two friends used to belong to a fantasy NBA league.
"He kicked me out of it," Moustakas said of Dominguez. "I wouldn't set my roster and he didn't like that too much. He wasn't even the commissioner, but he voted against me. I haven't been allowed back since. They keep it serious. I didn't even get invited to the play [in] their football league."
Gene Duffey is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.