Ernst, who is 6-foot-9 and 215 pounds, is the first recruit for new coach Steve Prohm. He is from Clinton, Iowa.
Ernst tore the ACL in his right knee in late February. But Ernst tells The Associated Press that he'll be able to resume basketball activities by late August at the earliest.
Ernst averaged 17 points and 13 rebounds a game last season and was the state's top-rated recruit, according to the website Prep Hoops Iowa.
Ernst had offers from a number of Missouri Valley schools, including Northern Iowa.