They are accused of providing funds and forged documents for the two men who posed as journalists and died when they detonated a bomb that killed Masud at the start of an interview with him in northern Afghanistan.
The eight are of Moroccan, Tunisian and Algerian origin but some have French citizenship. Their trial, which started on Tuesday, is expected to last until mid-April and they could face up to 10 years in jail.
The accused include 31-year-old Yusif al-Auni, a French of Moroccan origin, who investigators say has acknowledged belonging to a banned Islamist group.
Masud was the military and political leader of the National Alliance - the main opposition to the Taliban movement - which helped drive it from power after his death.
France's intelligence security service said the bomb killing Masud had been planted in a camera stolen from a journalist's car in the French Alpine city of Grenoble on 24 December 2000.
Investigating magistrate Jean-Louis Bruguiere has accused the eight of having links with a network of Islamist groups operating in France, Britain, Belgium and Italy which sent the two assassins to Afghanistan for training.