Four of the defendants were in court for the verdict and the remaining five, tried in absentia, were handed an 10 additional years in jail for failing to hand themselves in. Life imprisonment in Bahrain is a 25-year-sentence.
Monday's ruling brings to 104 the number of Shiites jailed since September 29 in connection with violence in the Sunni-ruled Gulf kingdom that began with the February 2011 uprising.
In court the four men had alleged that they were tortured, mistreated and held in solitary confinement, according to lawyers.
They were also convicted of making bombs and training others how to produce them, and "owning and using explosives for a terrorist purpose and carrying out bombings to terrorise citizens."
Bahrain's attorney general said that investigations proved the defendants were involved in "bombings" carried out on November 22, 2011, near the Exhibition Park in the capital Manama.
The attack damaged several cars but caused no casualties.
Today's ruling is the fifth tough sentence handed to Shiites since late last month.
These include a minimum 10-year jail term for an attempted bombing. If the attacks cause casualties, the sentence can be life imprisonment or the death penalty.
Bahraini Shiites continue to demonstrate in villages outside the capital and frequently clash with police.
At least 89 people have been killed since the protests began two and a half years ago, according to the International Federation for Human Rights.
Strategically located across the Gulf from Shiite Iran, Bahrain is home to the US Navy's Fifth Fleet and is an offshore financial and services centre for its oil-rich Gulf Arab neighbours.