Ali Oulkadi, who was imprisoned in France, drove Abdeslam across Brussels on November 14, the day after the attacks that killed 130 people, Belgian and French prosecutors told AFP.
That was the last trace of Abdeslam who then disappeared to become the world's most wanted fugitive before his spectacular capture in the Belgian capital four months later.
Abdeslam exonerated Oulkadi to investigators earlier this year, claiming his old friend knew nothing of the terror attacks.
French courts on Monday allowed Oulkadi to return to the Belgian capital where he resided before his arrest at the end of 2015.
Another man suspected of accompanying Abdeslam back to Brussels from Paris – Hamza Attou – has already been released, with a third, Mohamed Amri, still behind bars in France.
Amri and Attou are suspected of accompanying Abdeslam back to Brussels, getting him past three police checks in France before crossing the border into Belgium.