Jose Vilchis, 72, worked at I&M Gymnastics in southwest suburban Channahon.
The abuse happened between 2012 and 2013.
The jury in this case also heard evidence that Vilchis committed sexual crimes against three other teen girls, dating back to 1997.
SEE ALSO: Former Channahon gymnastics coach convicted of sexually assaulting teen girl
He was found guilty in June of eight counts of criminal sexual assault, the Will County State's Attorney's Office said in a news release.
The jury reached a verdict in less than two hours after a four-day trial.
"Jose Vilchis is a reprehensible sexual predator who calculatingly used his position of trust and authority to take advantage of innocent girls," Will County State's Attorney James Glasgow said in a statement. "He repeatedly preyed upon young gymnasts in private under the guise of being a caring coach. I commend these young women for their courage in coming forward and telling their stories. Although nothing can undo the damage he caused, he will spend the rest of his days in a prison cell unable to prey on anyone else."