After being released on bail, both men told media they didn't regret their actions and still believed it had been the right thing to do.
A third man, Nathan Law Kwun-chung, was also found guilty of inciting others to take part in an unlawful assembly. He told media he respected the court's decision.
Amnesty International Hong Kong Director Mabel Au said the verdict was a "blow to freedom of expression and peaceful assembly in Hong Kong."
The movement began after protesters, including Wong, stormed police barricades in September 2014 during a protest over a lack of democracy in elections for Hong Kong's chief executive.
The street protests lasted for two months and attracted up to 100,000 people at times, paralyzing the city's normally booming financial district. Both China's and Hong Kong's governments strongly disapproved of the protests.
Sentencing of the three men will take place on August 15.