The Texas Republican Party now endorses "reparative therapy" for gays, under a new policy statement given final approval at its annual convention.
The new anti-gay language never came up for debate before roughly 7,000 delegates ratified a Texas Republican Party platform that "tea party" groups succeeded in pushing further to the right, including winning a harder line on immigration.
One influential "tea party" group called Texas Eagle Forum had urged the party to support psychological treatments that seek to turn gay people straight.
It comes after the Republican governor of New Jersey, Chris Christie, signed a law last autumn banning such therapies on minors, and California enacted a similar law.
The Fort Worth Convention Hall cheered on Saturday when party leaders announced that Christie finished a distant 11th in a 2016 presidential straw poll.
"There's a very, very small group of people who want to keep the party in the past. We were here today to try to pull the party into the future," said Rudy Oeftering, vice-president of the gay conservative group Metroplex Republicans. "The only way the party can go into the future is to start listening to young people, to start listening to people who have gay family members."
Oeftering and allies had lined up to speak against the therapy language that had been added to the draft platform earlier last week.
But they never got a chance to address delegates, because a parliamentary motion to approve the full platform was called first.
Under the new plank, the Texas Republican Party recognises "the legitimacy and efficacy of counselling, which offers reparative therapy and treatment for those patients seeking healing and wholeness from their homosexual lifestyle".
The American Psychological Association and other major health organisations have condemned such counselling, which generally try to change a person's sexual orientation or to lessen their interest in engaging in same-sex sexual activity.
Gay conservatives did come away with a rare victory at the convention: winning the removal of decades-old language in the state party platform that states, "homosexuality tears at the fabric of society".