The decision follows a media outcry over the disqualification of Canadian contestant Jenna Talackova from the Miss Universe Canada contest because she was not a "naturally born female".
Talackova 23, who underwent gender reassignment surgery when she was 19, was reinstated to the competition last week by Donald Trump, who owns the Miss Universe organisation. Talackova has a Canadian passport, driver's licence and other documents that identify her as a woman.
Following consultations with the Gay and Lesbian Alliance Against Defamation (Glaad), Miss Universe "discussed a policy change that includes transgender women in time for the start of this fall's 2013 pageant season, a time when most of the competitions around the world begin to take place," the two groups said in a joint statement.
The change brings Miss Universe into line with other groups that have taken a stand against discrimination against transgender women, including the Olympics, the Girl Scouts of America and the TV show America's Next Top Model, Glaad said.
"We have a long history of supporting equality for all women and this was something we took very seriously," said Paula Shugart, president of the Miss Universe organisation.
The exact language of the new rule was still being worked out, officials said.
National pageants are currently being held around the world to chose contestants to compete in the 2012 Miss Universe contest, to be held later this year. Source: guardian.co.uk