Mohammed Ali Malek, 28, was convicted of multiple manslaughter, human trafficking and causing the disaster. He will face 18 years in prison.
His first mate, 26-year-old Syrian Mahmoud Bikhit, was sentenced to five years for facilitating illegal immigration.
The judge also ordered the men to pay £7.5million (€9million) each in compensation.
The two men were found guilty after their 90ft fishing boat sunk in the night between April 18-19, last year.
The boat had left Libya with more than 700 passengers onboard, most from sub-Saharan Africa and Bangladesh.
The boat came into difficulties shortly after its departure and sent out a distress call before accidentally crashing into a Portuguese cargo ship that had been coming to its aid.
Just 28 people survived the disaster, which has been described as one of the worst maritime disasters since the Second World War.
Despite claiming they had been forced to steer the boat by the real human traffickers, who supposedly died in the incident, the men were sentenced when their version of events did not match other survivors’ testimonies.
In a plea before the verdict, Malek told the court: “I spent two years and six months in Italy and I have a young son with an Italian woman: I want to marry her and recognise the baby.
“It’s the truth. I’ve always told the truth. Just as I immediately gave (police) my real name, and told them I was a passenger.”
The boat has since been recovered and towed back to Sicily after the first inspection of the vessel revealed decomposing bodies packed into every corner of the boat.
Forensic scientists spent months trying to count the victims and taking samples from passenger remains.
More than 175,000 migrants have arrived on Italy’s shores this year, the highest number anywhere in Europe.