In a series of moves announced prior to Wednesday's game, the Royals also recalled infielder Humberto Arteaga, activated left-handed pitcher Mike Montgomery, optioned right-hander Jake Newberry and traded outfielder Terrance Gore to the New York Yankees.
Mondesi injured the shoulder in the fifth inning of Tuesday's game against the Chicago White Sox when he attempted to make a diving catch on the warning track in shallow left field.
Royals manager Ned Yost said Mondesi will be evaluated in a week.
"He's sore today," Yost said. "I don't expect any decision right now. We'll just wait until we can give it some time to see how it feels."
Mondesi leads the major leagues in stolen bases (31) and triples (nine). The injury came 15 days after Mondesi returned to the Royals following his first stint on the injured list this season for a right groin strain.
Arteaga made his major league debut on June 20 and appeared in 11 games during Mondesi's first stint on the injured list.
Montgomery was acquired by the Royals on Monday in a trade that sent catcher Martin Maldonado to the Chicago Cubs and was activated Wednesday. Kansas City optioned Newberry to Triple-A Omaha to make room for Montgomery.
Montgomery, who was drafted by the Royals with the 36th overall pick in the 2008 draft, went 1-2 with a 5.67 ERA in 20 relief appearances for the Cubs this season.
The Royals plan to transition Montgomery into a starting role, something he is familiar with. Montgomery made 19 starts for the Cubs in 2018 and has started 56 games over the first four years of his career.
"I've been throwing every day, I've been throwing bullpens pretty much every other day the last couple weeks, even during the All-Star break," Montgomery said. "Physically, I feel good. I think it's just going to be a little bit of a trial."
Montgomery is scheduled to start Friday's game against Cleveland and the plan is for him to throw about 45 pitches and then gradually work his pitch count up after that.
Newberry has appeared in 16 games for the Royals this season while bouncing back and forth between Kansas City and Omaha. He is 1-0 with a 3.74 ERA this season.
The Royals traded Gore to the New York Yankees for $100,000. The Royals designated Gore for assignment Friday before trading him.
The speedy outfielder stole 13 bases in 37 games for Kansas City and hit .275 in a career-high 58 plate appearances.