The panel found 55-year-old Dan Goodwin guilty of two misdemeanors for his September climb up the Millennium Tower, one of San Francisco's tallest buildings.
Goodwin says he did it to bring attention to his claims that firefighters are unable to put out fires in high-rise buildings.
After the verdict, he disputed the way the judge handled his trial.
"They jury was really denied an opportunity to hear my side of the story," Goodwin said. "I was very limited as to what I could say and couldn't say. Every time I said something else, the jury was escorted out and I was scolded by the judge. It was very frustrating."
Goodwin will be sentenced next week. He faces a maximum punishment of a year in jail and a $1,000 fine.
