The convictions mark the broadest blow yet to suspected backers of the February 14 faction, named after the date in 2011 that an uprising began by Bahrain's Shiite majority seeking greater political rights from Sunni rulers.
The verdicts could stir more unrest in the strategic kingdom, home to the US Navy's 5th Fleet.
The main Shiite opposition party Al Wefaq called it a "black day for justice." Officials had no immediate comment on the court's decision.
Thousands of people have been arrested in Bahrain's crackdowns.