This is the second such ruling this week in the tiny Sunni-ruled Gulf kingdom, where members of the Shiite majority population have led an uprising.
The court also revoked the citizenships of the 23 convicts and fined two of them 200,000 dinars (USD 530,000/480,000 euros), terror crime prosecution chief Ahmed al-Hammadi said in a statement.
Judicial sources said that all the defendants were Shiite and that 16 were tried in absentia, without giving further details.
One of the bombings, in Damistan village, killed a Jordanian policeman working in Bahrain under a security and training exchange agreement.
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The other one in the nearby village of Karzakan, killing an elderly Bahraini man.
Both bombings were carried out by the same "terrorist group" formed by the defendants and "specialised in making explosives to target policemen," Hammadi said.
Meanwhile, an appeals court upheld the death sentence Thursday against a Shiite convicted of forming and leading a similar "terrorist group" that killed a policeman in a bombing in the Shiite village of Aker last year, Hammadi said.
Seven of them have been sentenced to life, and four others to 10 years, said Hammadi in a statement. The appeals court also approved revoking the citizenship of all the defendants convicted of attempting to kill three other policemen.
On Tuesday, Bahrain handed down sentences ranging from five years to life in prison to 29 people for the attempted murder of a policemen in a bombing later in December 2014.
Attacks against police are common in Bahrain, a Western ally and home to the US Navy's Fifth Fleet, across the Gulf from Iran.