Thomas has spent more than a year trying to clear his name after he was arrested and charged with murder.
Fifteen months ago, Thomas was charged with first-degree murder in the beating death of Reynaldo Ortiz, 50. A tip to police -- from alleged witnesses-- led to Thomas, a national light welterweight champion.
Thomas' lawyers say gang members blamed the boxer, who was 16 years old, because he refused to join them.
"He was blamed by five gang bangers for a murder he absolutely didn't commit," said Michael Oppenheimer, Defense Attorney.
Oppenheimer said those alleged gang members concocted a story about the killing and then phoned police.
"The police followed where the evidence led them. The gang bangers laid down those bread crumbs, and the police followed those bread crumbs. The bread crumbs, unfortunately, led to Semajay. Now he's been vindicated. He can go on with his life."
A jury found Thomas not guilty in less than an hour.
William Castillo was convicted in the killing and he now faces up to 60 years in prison. Jesus Duran is charged and awaiting trial.
"I lost it in the courtroom. They put us out. All I could do is fall on my knees, and I just thank God," said Carla Thomas, boxer's mother.
"My family, God, and boxing... all of that was my key, my key to how I stayed strong. Those were a tough 15 months," said Thomas.
Now the boxer is back in the gym- and hoping to go for the gold in the 2018 Olympics. He continues to follow his Olympic dreams instead of falling into gang life. It's a message he wants to share with other young people.
"You don't have to be in a gang to be somebody. You don't have to be in a gang to get what you want for your family. You don't have to sell drugs. You can use your talent. You're God given talent and become successful - everyone has a talent," said Thomas.
"Boxing is my ticket...my way of succeeding in life and doing the things I want to do and making a way for my family to do the things they want to do," said Thomas. "That's why it's so important for me to become champ - the champion - and do something with my life."
The Cook County State's Attorney's Office said two witnesses who previously identified Thomas recanted their testimony on the stand. The state's attorney's office says it respects the jury's decision but stands by its decision to prosecute the case.
Thomas enrolled in school this week and has a golden gloves tournament in February.