The defendant Arnaud Djender, who is white himself, admitted taking part in the assault but denied having racially insulted the victim.
The court sentenced him to three years in prison with the additional sanction that the sentence should start immediately.
Djender joined in when another man attacked the victim at Paris's Gare du Nord in September 2010.
Witnesses say at least one of the assailants shouted "dirty white" and "dirty Frenchman" as they ran off afterwards, leaving the victim with injuries that meant he was off work for 39 hours.
"There is absolutely nothing that establishes that my client pronounced a single racist insult, least of all an anti-white one, which would be absurd given that he is white himself," Djender's lawyer, Grégoire Etrillard, told reporters.
Prosecutors had called for a setence of four years, one suspended, claiming that the crime was racially aggravated.
The anti-racist campaign Licra, which joined the prosecution claiming that anti-white racism is a "social phenomenon", has called on them to appeal against a judgement it described as "open to criticism".
The court accepted that there had been a racist act, Licra's lawyer, Mario-Pierre Stasi, said, but attributed it to the other assailant, who has not been found.
Mainstream right-wing politician Jean-François Copé caused controversy last year when he published a book claiming that racism against whites was on the rise in France, a claim previously made by the Front National's Marine Le Pen.