The three activists - Albert Ho, Lee Cheuk-Yan and Chow Hang-Tung - have all previously been convicted of participating in or organising the pro-democracy protests.
All three have also been detained since 2021 awaiting Friday's verdict, a period that will count towards their sentences of between five years and seven years and three months.
The UN, the EU and several individual countries have condemned the sentences handed down under the city's draconian security laws, which Beijing pushed through in 2020 to end the protests.
