Team China, which captured the gold medal in men's basketball at the 2018 Asian Games, previously participated in the 2007 Summer League. It's the first appearance for Team Croatia, which reached the quarterfinals at the 2016 Summer Olympics.
The Croatian national team features several NBA players, including Dario Saric of the Minnesota Timberwolves, Bojan Bogdanovic of the Indiana Pacers and Mario Hezonja of the New York Knicks.
It's unclear whether the Summer League roster will include the team's full roster or a younger group of developmental players similar to what all 30 NBA teams send to Vegas, though.
The 2019 edition of the Vegas event will feature 83 games across 11 days. The Portland Trail Blazers are the defending champions after beating the Los Angeles Lakers, the 2017 champs, in the final.
This year's tournament could feature a high-profile group of elite prospects, led by Duke Blue Devils Zion Williamson and RJ Barrett as well as Murray State Racer Ja Morant.
The 2019 NBA draft takes place June 20 to determine those rising stars' NBA homes.