Nemmouche, wearing a blue sweater, spoke only to confirm his identity as the hearing began at 10:30 am (0930 GMT).
"Nemmouche, Mehdi, 33 years old, unemployed," he told the criminal court in Brussels before it selected a jury of eight men and four women for the trial, which opens on Thursday.
More than 100 witnesses are due to testify at the trial, which will be attended by the victims' families and Jewish community leaders, who have denounced the anti-Semitic nature of the attack.
And more than 300 Belgian and foreign journalists have registered to cover the proceedings which could last until the end of February.
The deadly attack, which lasted only 82 seconds, shocked Belgium and the world.
Firing a pistol and then an assault rifle, the gunman killed two Israeli tourists, a French volunteer and a Belgian receptionist at the Jewish Museum.
Nemmouche -- born to a family of Algerian origin in the northern French town of Roubaix -- was arrested six days after the attack.
He was caught in the southern French port city of Marseille after arriving on a bus from Brussels, carrying a handgun and an assault rifle.
Before the attack, Nemmouche is said to have fought in Syria as part of a jihadist faction and is also accused of acting as a jailer of kidnapped French journalists.
Investigators say he was in Syria from 2013 to 2014, where he met Najim Laachraoui, a member of the gang which went on to carry out suicide bombings in Brussels that killed 32 people in March 2016.
That same Brussels cell is also alleged to have coordinated and sent jihadists to carry out the Paris massacre of November 13, 2015, in which 130 people were killed and hundreds more wounded.
Both attacks were claimed by the Islamic State (IS) group, whose activities in Syria and Iraq lured thousands of jihadists from Europe.
Nemmouche and Bendrer, investigators say, met nearly a decade ago while in prison in southern France, where they were both described as "radicalised" inmates who tried to win others over.
Bendrer was arrested in Marseille seven months after the Jewish Museum attack and charged as Nemmouche's accomplice.
Although he was jailed for five years in September by a French court for attempted extortion, he was transferred to Belgium for the trial.
Nemmouche is expected to face a separate trial in France for holding French journalists hostage in Syria.
The former hostages are expected to testify about Nemmouche's character during the Brussels trial, despite the defence arguing that theirs is a separate case.
Belgian Jewish leader Yohan Benizri told AFP he feared Nemmouche's lawyers Sebastien Courtoy and Henri Laquay will try to "play down" the anti-Semitic nature of the museum attack.
The defence team, Benizri added, may even try to "twist" the facts by repeating "totally far-fetched" claims that Israel's intelligence service Mossad staged the attack.
"We don't want Mehdi Nemmouche to become a star. He is a terrorist," said Benizri, who heads the Belgian Federation of Jewish Organizations.
Courtoy himself suggested Israeli agents could be behind the attack when he spoke at a pre-trial hearing on December 20.
While Jewish groups say the evidence against Nemmouche is "overwhelming," Courtoy argued "a trap" was sprung on his client.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)
Business Standard has always strived hard to provide up-to-date information and commentary on developments that are of interest to you and have wider political and economic implications for the country and the world. Your encouragement and constant feedback on how to improve our offering have only made our resolve and commitment to these ideals stronger. Even during these difficult times arising out of Covid-19, we continue to remain committed to keeping you informed and updated with credible news, authoritative views and incisive commentary on topical issues of relevance.
We, however, have a request.
As we battle the economic impact of the pandemic, we need your support even more, so that we can continue to offer you more quality content. Our subscription model has seen an encouraging response from many of you, who have subscribed to our online content. More subscription to our online content can only help us achieve the goals of offering you even better and more relevant content. We believe in free, fair and credible journalism. Your support through more subscriptions can help us practise the journalism to which we are committed.
Support quality journalism and subscribe to Business Standard.