The band posted the announcement of his death on its web site and on its Facebook page.
"The members of Twisted Sister are profoundly saddened to announce the untimely passing of our brother, AJ Pero," said the post.
"The band, crew and most importantly the family of AJ Pero thank you for your thoughts and prayers at this time."
Dee Snyder posted on Twitter: "My friend, my brother, my band mate passed away today. My heart is broken. RIP A.J. Pero."
Pero was 55.