Seven women and five men took 30 minutes to reach the verdict.
After the verdict was read, the teenager collapsed in his chair and tears started streaming down his face. His mother shouted out 'no' repeatedly and left the courtroom crying.
The boy, who will be sentenced next month and could be imprisoned until he is 21 years old, is the first defendant to be tried in the Albert case. The trial progressed quickly, with opening statements beginning on Tuesday and closing arguments wrapping up a day later.
"We're pleased with the verdict, but because there are pending cases, that's the only comment that we can give at this point," said Lisa Morrison, assistant state's attorney.
In closing arguments, prosecutors referred to the video that captured the September 2009 melee in which Derrion Albert, 16, was hit with a wooden plank, punched and kicked. "He's not mixed up in the brawl. He's the one mixing it up," they said of the defendant. Prosecutors also said the punch he delivered to Albert, "signed his death certificate."
The defendant's attorney admits that his client punched Albert but said there was no way to determine that his was the fatal blow.
"I don't think it's appropriate that he got found guilty, a 14-year-old boy, considering what he did and considering that there was an intervening event that happened after he got involved," said defense attorney Richard Kloak.
The prosecution's final witness was the forensic pathologist who performed the autopsy on Albert. She said the cause of death was cerebral injuries due to blunt trauma. She also explained Albert had hemorraging and extensive swelling of the brain.
The defense did not present any witnesses and said they plan to appeal the verdict.
Some of Albert's family members entered the court building Wednesday morning wearing buttons depicting the deceased teenager on their coats.
"He's been very obtuse throughout this whole thing, and I believe he thought that he couldn't be found guilty, so I think it was an act," said Norman Golliday, Albert's grandfather. "I don't know how we get through it. We pray every day."
Four other teens have been charged as adults in the murder: Silvonus Shannon, Eugene Riley, Eric Carson and Lapoleon Colbert. Their trials are scheduled to begin in the new year.
All of the suspects are seen on a violent cell phone video that captured the September 24, 2009 mob brawl and sparked a national debate on youth violence.
The video was played in court during the trial. Muffled sobs were heard from family members of the 16-year-old Fenger high school honor student as they watched the video of him being attacked by the group of teenagers.
The video-recorded fight among at least 50 teenagers stemmed from a long standing rivalry between two groups of students at Fenger High School.