The 6-foot-10, 200-pounder from Australia, now playing his prep ball at Montverde (Fla.), gave his pledge to Johnny Jones and the Tigers after taking an unofficial visit to LSU on Saturday.
"I pretty much made up my mind yesterday, but I wanted to sleep on it," Simmons told TSD.
Simmons, who turned down the likes of Duke and Kansas, also confirmed he is done with his recruitment.
"I will take an official visit to LSU with my parents, but that is it," he said. "LSU just felt like family and like home."
Currently Simmons is the No. 2 power forward and the No. 8 overall prospect in the Class of 2015, as rated by Scout.com.
Ben Simmons commits to LSU