His lawyer Michael Proctor confirmed the actor, 35, who pleaded guilty to the charges in December, was found dead in Los Angeles.
However, he did not reveal the cause of death.
In a statement, Mr Proctor said: “I can confirm that Mark Salling passed away early this morning.
“Mark was a gentle and loving person, a person of great creativity, who was doing his best to atone for some serious mistakes and errors of judgement.”
A law enforcement official told The Associated Press that Salling was found near a riverbed in Tujunga and the death is being investigated as a suicide.
Both TMZ and Hollywood Reporter cite police sources who have confirmed the death as a suicide to them.
The performer, who rose to fame playing Noah “Puck” Puckerman in the hit television series, was due to be sentenced on 7 March.
Prosecutors in his case said a search of Salling’s computer found more than 50,000 child abuse images.
He was facing between four and seven years in prison before 20 years of supervised release, with conditions to be set by the court.
Before starring in Glee, which aired between 2009 and 2015, the actor had only appeared in a handful of shows and films.
They include a 1999 appearance in the Chuck Norris series Walker, Texas Ranger. He also appeared in the 1996 film Children of the Corn IV: The Gathering and 2014 TV film Rocky Road.
As a singer-songwriter, he released two albums – Smoke Signals in 2008 and Pipe Dreams in 2010.
Salling’s death comes after the death of his former Glee co-star Cory Monteith, who played Finn Hudson in the show.
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A coroner ruled Monteith died in 2013 from a toxic mix of alcohol and heroin.
:: Anyone feeling emotionally distressed or suicidal can call Samaritans for help on 116 123 or email email@example.com