Chastity Bono is thought to have begun the process of changing his gender from female to male shortly after his 40th birthday earlier this year.
Speaking to TMZ, his publicist announced that "after many years of consideration", the writer and activist had "made the courageous decision to honour his true identity".
"He is proud of his decision and grateful for the support and respect that has already been shown by his loved ones.
"It is Chaz's hope that his choice to transition will open the hearts and minds of the public regarding this issue, just as his 'coming out' did nearly 20 years ago."
Bono previously discussed his parents' reaction to his sexuality in the book Family Outing, admitting that while Sonny was fine about his decision, Cher took the news badly and banished him from her New York home, although the pair later reconciled.