It requires social workers for grades 7 through 12 to undergo suicide prevention training.
Currently, only guidance counselors and teachers have to take part in such training.
The law is known as the Jason Flatt Act. It is named after a 16-year old who took his own life.
His father, Clark Flatt, said Illinois is the fifth state to pass a law such as this.
"I can guarantee you because of this act, Governor, there will be a young person alive 12 months from now that would not have been alive without this law - and how important is that?" said Flatt. "If that young person is your son, your daughter, your grandson or your granddaughter, as they say on the commercial, it's priceless."
According to the Centers for Disease Control and Prevention, suicide is the third leading cause of death among young people.