He homered off former Kansas City teammate Johnny Cueto and added an RBI single in the contest played at San Diego's Petco Park.
The second-inning home run made him the first Kansas City player to go deep in an All-Star Game since Bo Jackson in 1989 and tied the game at 1-all. Then, his one-hopper off Kris Bryant's left arm on a pitch from Jose Fernandez in the third made it 4-1.
Hosmer won a truck as part of being named MVP and said he was giving it to his dad, Michael, who stood off to the side.
"So he can stop stealing all my cars,'' Hosmer said.
Hosmer and Royals teammates Salvador Perez and Kelvin Herrera made sure Kansas City will start at home if it gets a chance to defend its World Series title. The AL will open the Series at home for the 11th time in 14 years since the All-Star Game winner was used to determine the host for Games 1 and 2.
"Hopefully, this is something we can all rally upon for the second half and find a way to use that home-field advantage,'' Hosmer said.
Kansas City is languishing at 45-43, seven games off the AL Central lead and in the middle of the wild-card race as attention turns to which teams will be buyers and sellers as the Aug. 1 trade deadline approaches.
"We know how much that home-field advantage helped us,'' Hosmer said. "It just brings that sense of comfort to the team and gives you a jump-start for the whole Series.''
The team with home-field advantage has won the World Series six of the past seven times and 24 of the past 30.
Information from The Associated Press was used in this report.