Sixteen defendants were handed 15-year terms, while four others were jailed for 10 years and the other 30 sentenced to five years behind bars, the source said, AFP reported.
The defendants, including Iraqi cleric Hadi al-Mudaressi who was sentenced in absentia, were charged with forming the February 14 Revolution Youth Coalition, which Bahraini authorities accuse of "terrorism".
Several defendants were sentenced in absentia, including Saeed al-Shahabi, a key London-based Bahraini opposition figure who faces an earlier life sentence for his role in the 2011 uprising.
The interior ministry in June named 11 suspects who were arrested in the case, in addition to 13 people who live abroad.
At least 89 people have been killed by the Bahraini authorities since peaceful protests erupted In February 2011, according to the International Federation for Human Rights.