The 31-year-old said that he has felt like he was in the wrong body ever since he was a child.
Gabel is planning to take hormones and undergo electrolysis treatments in the next few months and is also considering gender reassignment surgery.
‘Growing up, my experience with transsexualism was nothing but shame,’ he told Rolling Stone magazine.
Gabel insists he is not attracted to men and will continue to stay married to Heather, the mother of his two-year-old daughter. He said he had been worried about how his wife would react to the news but claims she has been incredibly supportive.
He explained: ‘For me, the most terrifying thing about this was how she would accept the news.
‘But she’s been super-amazing and understanding.’
Asked why he had gone public with the news, Gabel said: ‘I’m going to have embarrassing moments and that won’t be fun.
‘But that’s part of what talking to you is about – is hoping people will understand, and hoping they’ll be fairly kind.’
Against Me! are due to go on tour with The Cult later this month.