Judge Marie-France Keutgen told the courtroom that 28-year-old Abdeslam and Tunisian Sofien Ayari, 24, had been found guilty of “attempted terrorist murder” during the shootout in March 2016.
Abdeslam is in a French prison awaiting trial for his role in the Islamic State attacks in Paris in November 2015 in which 130 people were killed. Prosecutors say he is the lone survivor of a suicide squad.
Abdeslam was born in Brussels from Moroccan parents who also had French nationality. This allowed him to become French himself.
He was involved in petty crime in Belgium as a youth, and is believed to have become radicalised along with his brother Salim around 2014.
Both then reportedly joined a French-Belgian network linked with the Islamic State group (IS), which later claimed the Paris attacks.
The network was involved in both the Paris attacks and bombings that struck the Brussels metro and airport on 22 March 2016, just days after Abdeslam’s arrest, killing 35 people.
In Monday’s ruling, the court denied a request by victims from those attacks that they be regarded as a civil party to the case, saying no link had been established with Abdeslam and Ayari.
He is believed to have played a key role on 13 November 2015 – when militants targeted a concert hall, stadium, restaurants and bars, killing 130 people and injuring hundreds more.
French prosecutors believe Abdeslam helped the jihadists by hiring cars, flats and hotel rooms – although his role in the actual shootings and bombings is unclear.
His brother Salim was among the attackers and blew himself up outside a cafe.
Salah Abdeslam and two associates drove from Paris to Brussels the next day. They were stopped by police at a border check, but were allowed to travel as he had not yet been identified as a suspect.
French and Belgian authorities released Abdeslam’s photo and name a day later – by which time he was one of Europe’s top fugitives.
Several flats were raided by Belgian police over the next few months. He was finally picked up on 18 March 2016.