There were no noted dissents from the court's one-sentence order.
Similar age verification laws have passed in other states, including Arkansas, Indiana, Kansas, Louisiana, Mississippi, Montana, Oklahoma, Utah and Virginia.
The Texas law carries fines of up to $10,000 per violation that could be raised to up to $250,000 per violation by a minor.
Last year, a federal judge blocked the law's age verification requirement and health warnings, finding that they likely violated the Constitution. But in March, a divided panel of the 5th U.S. Circuit Court of Appeals reversed the age verification ruling, although it upheld the health warnings ruling that adult sites can't be forced to publish statements with which they disagree.
The health warnings, disputed by the industry, included that pornography is addictive, impairs mental development and increases the demand for prostitution, child exploitation and child sexual abuse images.