The singer had retired from the band two years ago.
Smash Mouth lead singer Steve Harwell died Monday at his home in Boise, Idaho. He was 56.
Harwell had "many health issues," and died from acute liver failure, the band’s manager Robert Hayes confirmed.
The "All Star" singer, who retired from the band two years ago, died peacefully, surrounded by family and friends, Hayes said.
"Steve Harwell was a true American Original," Hayes said. "A larger than life character who shot up into the sky like a Roman candle."
Harwell retired from the band after a concert in upstate New York about two years ago, where he was heard slurring his words and making vaguely threatening comments toward the audience, according to Variety.