The sentence was tougher than that sought by prosecutors against the 33-year-old star over the 2015 extortion attempt, which led Benzema to be cast out of the France team for five-and-a-half years.
Benzema was not in court in the Paris suburb of Versailles for the verdict, which comes hours before Real Madrid take on Sheriff Tiraspol in a Champions League game in Moldova.
He was not accused of being behind the extortion attempt but rather of conspiring with the suspected blackmailers by putting pressure on Valbuena to pay them off.
The court ruled that he had “implicated himself personally, through subterfuge and lies, to convince his team-mate to submit to the blackmail.”
It added that he had shown “no kindness towards Valbuena”, as he had claimed, “just the opposite” and had even appeared to take pleasure in his fellow player’s demise.
His defence team immediately announced plans for an appeal.
Speaking to reporters at the courthouse, one of his lawyers, Sylvain Cormier, said he was “stunned” by the sentence which he called “very severe, unfair and unfounded”.
A second lawyer, Antoine Vey, said that Benzema, who did not attend his trial, would “come and explain himself” when the case went to an appeal.
The prosecution had called for Benzema to be given a 10-month suspended sentence.