Robbins reportedly died by suicide.
The Los Angeles native began his career as a child performer.
He's best known for his work in the 1960s, voicing the lovable sad sack in "It's the Great Pumpkin, Charlie Brown," "A Charlie Brown Christmas," and more.
Robbins had a history of addiction and mental health struggles, which he spoke about openly.
In December 2015, Robbins was sentenced to nearly five years in prison for making criminal threats. He was released in 2019.
If you or anyone you know needs help, the National Suicide Prevention Lifeline provides free, confidential support for people in distress, prevention and crisis resources for you or your loved ones.