The defendants are former legislators Lee Cheuk-yan, Leung Kwok-hung, Albert Ho, Yeung Sum, Cyd Ho, Sin Chung-kai, Apple Daily founder Jimmy Lai, and activists Figo Chan, Avery Ng and Richard Tsoi.
Ng and Tsoi also admitted in the District Court to another count of taking part in the National Day protest.
The same charge against the rest of the defendants was not pursued and was left on the court’s file.
Chan, Lee, Leung and Albert Ho also pleaded guilty to inciting others on September 30, 2019, to take part in the rally.
Judge Amanda Woodcock will hear mitigation pleas on May 24 and deliver the sentences on May 28.