Six others were handed 10 years in jail each for their role in the unrest, General Prosecutor Ahmed al-Hammadi said.
The nine were tried for attempted murder of police officers, possessing explosive and participating in clashes in March 2014, Hammadi said, according to the official Bahrain News Agency.
Bahrain last month sentenced eight people to life in jail for "terrorism" and violence against security forces in January last year.
The tiny Gulf state has been shaken by unrest since it quelled a month-long, Shiite-led uprising demanding reforms in 2011.
Despite the crackdown on the 2011 uprising, protesters frequently clash with police in Shiite villages outside the capital Manama.