Foreign ministry spokesman Bahram Ghasemi condemned Thursday night's shooting that killed a policeman on the world-famous Champs Elysees avenue and expressed sympathy with the French people, the ISNA news agency reported.
But he added: "Unfortunately, concessions and at times supportive actions for brutal terrorists indicate a double standard by the Western world in dealing with terrorism, and have made terrorists bolder."
Iran has repeatedly accused Western governments of directly or indirectly supporting terrorists through their backing for rebels fighting to overthrow Syrian President Bashar al-Assad.
Shiite-majority Iran strongly supports Assad against Sunni terrorists such as the ISIS group, which claimed responsibility for Thursday's attack.
It labels all rebels fighting against Assad's forces as "terrorists".
"Once again we reiterate that terrorism is the first and most urgent danger for peace, stability and global security," Ghasemi said.