The court decision comes as some opposition groups, inspired by Egyptian crowds that helped topple President Mohammed Mursi, are calling for stepped-up protests.
Lawyer Mohamed al-Wasti said today the group was convicted of trying to bypass security cordons last year to reach Pearl Square, the hub of protests in early 2011.
Al-Wasti said the protesters plan to appeal yesterday's court ruling.
Bahrain has faced nearly 29 months of unrest as Shiite-led protesters seek a greater political voice in the strategic Sunni-ruled kingdom, which is home to the US Navy's 5th Fleet.