Brian Shivers has been found guilty of murdering two British soldiers outside Massereene Barracks in Antrim in 2009.
Prominent dissident republican Colin Duffy was earlier acquitted of the murders.
Sappers Patrick Azimkar from London and Mark Quinsey from Birmingham were killed outside Massereene Barracks on 7 March 2009.
Four others, including two pizza delivery men, were seriously injured in the attack, for which the Real IRA claimed responsibility.
Mr Duffy, 44, and Shivers, 46, denied having any involvement in the attack.
The evidence against Shivers centred on DNA which was discovered on a mobile phone and matches linked to the getaway car.
During his trial his lawyers described him as an "unlikely terrorist".
The 46-year-old, who has cystic fibrosis, told the court he had a limited life span and had been told by a doctor that he only had a few years left to live.
Handing down the judgment in Belfast Crown Court Mr Justice Anthony Hart said Shivers lied about his actions on the night of the attack.
The judge said the presence of his DNA on the Nokia phone was further evidence of his involvement in the getaway car.
Shivers was sentenced to life in prison.
Colin Duffy acquitted
Mr Duffy, from Forest Glade in Lurgan in Armagh, was cleared of all charges by Mr Justice Anthony Hart this morning.
Judge Anthony Hart told the court he was satisfied that Duffy's DNA was found on a latex glove tip inside the car - and on a seat buckle - but he said the prosecution had failed to link the defendant to the murder plot.
He said "all the evidence" suggested Mr Duffy was present in the getaway car wearing latex gloves at some point between the time it was bought and the time it was used in the attack.
But the judge said that suspicion that the car was going to be used in a criminal act was not enough to convict Mr Duffy.
The judge described the attack as "ruthless and determined". He said one of the gunmen had reloaded his weapon at the scene and that a number of the victims were shot as they lay injured on the ground.
Following Mr Duffy's acquittal, Mr Justice Hart cleared the court of a number of cheering supporters.
Before the judgments were handed down, the parents of one of the two murdered soldiers spoke of their son's love for Northern Ireland.
Speaking from their home in England earlier this week, Mehmet and Geraldine Azimkar said Patrick wanted to build a life there when his time in the military was over.
The Azimkars said their son had wanted to become a carpenter and joined the British Army in the hope of gaining skills in a trade.