More than 10 other people were inside the premises in Mong Kok.
Kowloon City Magistracy said it accepted that Chan, who was a Civic Party lawmaker at the time, was explaining the relevant social distancing rules to bar owners.
It said the meeting was designed to convey information to help contain Covid-19 and was therefore not subject to the four-person public gathering limit imposed by the authorities.
Magistrate Cheng Lim-chi also acquitted Gordon Lam, the convenor of the Small and Medium Restaurant Federation, of the same charge of participating in a prohibited group gathering.
Chan Wai-choi, who was in charge of the bar, was cleared of allowing the gathering to take place, but was convicted of an offence for not checking people’s temperatures before they entered the premises.