Clark County coroner spokeswoman Samantha Charles confirmed the cause Monday after toxicology results were received Monday.
Dubrow was found dead Nov. 25 at his Las Vegas home. He was 52.
Quiet Riot was perhaps best known for its 1983 cover of "Cum on Feel the Noize." The song, featuring Dubrow's powerful, gravelly voice, appeared on the band's album "Metal Health" -- which was the first by a metal band to reach No. 1 on the Billboard chart.
DuBrow recorded a solo album in 2004, "In for the Kill," and the band's last studio CD, "Rehab," came out in October 2006.