Joshua Wong Chi-fung was among four people who pleaded guilty on Friday to participating in an illegal assembly in Hong Kong last year.
Wong, who is already in prison after he was found guilty of participating and organizing an unauthorized assembly in 2019, appeared in the District Court.
The others pleaded guilty were Lester Shum, Jannelle Leung and Tiffany Yuen. Eddie Chu, asked for an adjournment, and his case will be heard on June 11.
Nineteen others facing similar charges.