When asked by the warden if he had a final statement, Beazley looked toward Suzanne Luttig, the daughter of the victim, and said "no" before he was given a lethal injection.
Beazley was convicted of killing the father of a federal judge during a 1994 carjacking. He repeatedly expressed remorse for shooting John Luttig, 63, while trying to steal the man's Mercedes.
"It's my fault," Beazley, 25, said during a hearing last month. "I violated the law. I violated this city, and I violated a family — all to satisfy my own misguided emotions. I'm sorry. I wish I had a second chance to make up for it, but I don't."
Texas is one of five states that allow the death penalty for crimes committed by 17-year-olds.
Before Tuesday, 18 inmates in the United States — including 10 in Texas — had been executed since 1976 for a murder committed when the killer was younger than 18.
"Texas must recognize that the brutal practice of executing children is in complete and utter defiance of international law," said Sue Gunawardena-Vaught, director of Amnesty International USA's Program to Abolish the Death Penalty.
In Austin, about 100 death penalty opponents rallied at the governor's mansion to protest Beazley's execution.
Earlier Tuesday, the Texas Board of Pardons and Paroles voted 10-7 against recommending that Beazley's sentence be commuted to life in prison and 13-4 against a reprieve.
Beazley's lawyers made a last-ditch appeal to the U.S. Supreme Court, renewing questions about his age and challenging the makeup of the all-white jury that convicted their black client. The court turned down the appeal, and Gov. Rick Perry denied his request for a 30-day reprieve.
"To delay his punishment would be to delay justice," Perry said.
Luttig was the father of J. Michael Luttig, a judge on the 4th U.S. Circuit Court of Appeals and former clerk or adviser to Supreme Court Justices Clarence Thomas, David Souter and Antonin Scalia. All three did not participate in high court rulings on Beazley's case.
At the time of the slaying, Beazley was a popular student and athlete in Grapeland, where he had also been dealing drugs for several years. Prosecutors said he and two companions ambushed Luttig and his wife.
Beazley shot Luttig once, turned the gun on his wife but missed, then returned to the wounded man and fired again point-blank into Luttig's head. He stepped through a pool of blood to go through the man's pockets to get the car keys. He hit a wall while driving away and was forced to abandon the damaged vehicle.
The two companions received life in prison.