Traces of the 23-year-old's DNA were detected on the butt of the Kalashnikov used by Karim Cheurfi when he gunned down a police officer on April 20th, injuring two other policemen as well as a German woman, before being shot dead by police.
The man, who was detained on Monday in the Paris region and has been jailed pending trial, was previously unknown to French anti-terrorist investigators.
He has been charged with criminal terrorist conspiracy and using a weapon linked to terrorism, the source said.
The suspect, who was not named, is the first to be charged in the April 20 shooting. He had told investigators he did not know 39-year-old Cheurfi, the source added.
The evening attack on the busy Paris avenue took place days before the first round of France's presidential election.
A note praising the Islamic State group was found next to the body of Cheurfi. Police later found other weapons in Cheurfi's car including a shotgun and knives.
The Islamic State group claimed the shooting as the work of one of its “fighters”. It was the latest in a string of attacks that have claimed 239 lives around France since 2015.
However, the IS named the shooter as Abu Yussef the Belgian, which does not correspond to Cheurfi, who was from the eastern Parisian suburbs.