Final Senate adoption of the bill was possible later on Tuesday or Wednesday. The measure would then be sent to the state House of Representatives, where passage during a 30-day special legislative session that ends in mid-August is less certain despite a Republican majority in that body as well.
Enactment in Texas, the most-populous Republican-dominated state, could give momentum in other socially conservative states for additional action on an issue that has become a flashpoint in the U.S. culture wars.
Under the Texas measure, known as Senate Bill 3, restrooms, showers and changing facilities in schools and other public places "must be designated for and used only by persons of the same sex as stated on a person's birth certificate."
Supporters, including Republican Lieutenant Governor Dan Patrick, a staunch social conservative, have said the legislation promotes public safety and protects vulnerable women and children.
Momentum for so-called bathroom bills stalled earlier this year when a similar law in North Carolina was partially repealed in March. The original law prompted boycotts by a number of athletic organizations and businesses that were estimated to have cost the state hundreds of millions of dollars.
