Lawyer Sefen Guez Guez told AFP news agency on Monday that he was looking at launching an appeal.
The 29-year-old working for a firm subcontracted by energy giant EDF had been granted access to nuclear installations as part of his job throughout 2012 and 2013.
But in March this year, the man - who cannot be named according to French law, had his pass to enter the Nogent-sur-Seine nuclear power station revoked.
Officials said he had links with a violent armed group and that he was in touch with an imam involved in recruiting people to fight in Iraq.
A court in the north-eastern town of Chalons-en-Champagne upheld the ban saying the management could prevent those "undergoing a process of political and religious radicalisation" from accessing sensitive sites.
The lawyer for the man cried foul and argued that his client had no police record.
France bans Muslim worker from nuclear sites - Europe - Al Jazeera English (external - login to view)