Youssef Siraj is suspected of having housed Ayoub El Khazzani in Brussels who allegedly shot and seriously wounded a Thalys passenger before being overpowered.
"In connection with the investigation into the terrorist attack on the Thalys of 21 August 2015, Youssef S. has been handed over today to the French judicial authorities," the federal prosecutor's office said.
Youssef and Mohamed Bakkali, who had been in custody in Belgium charged with helping to organise the Paris attacks, were charged in Brussels last October with helping Khazzani in the train attack.
Brussels handed Bakkali over to French authorities last week on condition that he would serve any eventual sentence in Belgium.
France immediately charged Bakkali with being an accomplice in the November 13, 2015 attacks which left 130 people dead and hundreds wounded across Paris.
Several men from the Brussels neighbourhood of Molenbeek are alleged to have taken part in those attacks.
Youssef Siraj, a Molenbeek resident, is alleged to have housed Khazzani, a Morrocan, shortly before the Thalys attack.
A bloodbath was only narrowly averted on the Thalys train from Amsterdam to Paris when passengers including two off-duty US servicemen subdued Khazzani -- who had fought for the Islamic State group in Syria -- as he opened fire with a Kalashnikov.
Khazzani, a Moroccan who fought for Islamic State in Syria, has allegedly told investigators he was acting on the orders of Abdelhamid Abaaoud, one of the organisers of the Paris attacks, whom he met in the war-torn Middle Eastern country.
The Thalys incident added further weight to the theory that the French-Belgian IS network had been behind the Paris attacks in 2015 and triple suicide bombings in Brussels in March the following year.
Khazzani is one of three people France has charged in the Thalys case, along with Bilal Chatra and Redouane Sebbar.
Chatra is suspected of having played the role of scout for Khazzani on the migrant trail to Europe from Syria. Sebbar is believed to have helped prepare the train attack.