The jury deliberated for four hours before returning the verdict against David Henry Tuck, 18, who could be sentenced to life in prison.
Prosecutors said the attack was racially motivated in part because the 17-year-old victim is Hispanic and Tuck espoused white-supremacist beliefs.
Authorities said Tuck shouted racial insults as he punched, kicked and stomped the teen for four to five hours and sodomized him with the plastic pole of a patio umbrella. Tuck and another teen later stood him against a fence and poured bleach all over him, according to investigators.
Doctors did not initially expect the boy to live. He was hospitalized for more than three months and underwent 20 to 30 surgeries. He testified Wednesday that he remembered nothing of the assault.
"They wanted to kill him, violate him in any way they could," prosecutor Mike Trent said in closing arguments. "This man is guilty of about the most heinous crime you will ever see where the victim survived."
Defense attorneys blamed two witnesses to the attack, a 16-year-old boy and his 13-year-old sister who hosted the party at their family's home in the Houston suburbs. Testimony indicated the youths drank alcohol, smoked marijuana, snorted cocaine and took the anti-anxiety drug Xanax.
During the trial, Gus Sons and his sister testified that they watched helplessly as Tuck and the other teen assaulted the victim.
The two siblings said the attack was triggered by the victim's drunken attempt to kiss Danielle Sons and by an alleged attempt by the victim to steal drugs from Gus Sons.
Defense attorney Chuck Hinton told jurors the attack was not racially motivated, despite testimony about swastikas on Tuck's possessions.
"That's not what this case is about," he said. "It's about a bunch of guys all messed up on drugs and someone wound up getting hurt."
The jury was to begin hearing testimony Friday in the sentencing phase of the trial.
The other teen charged in the beating, Keith Robert Turner, 17, is set to go to trial next month.
The Associated Press has not identified the Hispanic teen because he is a juvenile sexual assault victim.