Benzema was charged by a court in Versailles this month with complicity in an attempt to blackmail and participating in a criminal conspiracy as part of an investigation into an alleged plot to extort money from Valbuena.
Sylvain Cormier - Benzema's agent - has protested his client's innocence, stating the Real Madrid striker is "absolutely calm and beyond reproach", while Valbuena broke his public silence on the incident on Friday.
He told Le Monde he was "more than disappointed" with Benzema's behaviour.
The FFF confirmed later Friday it was to bring a civil action in the case, with parties in French law able to make claims for compensation if they feel they have suffered damage or injury.
The organisation said in a statement: "The French Football Federation has decided to be Partie Civile in the Karim Benzema/Mathieu Valbuena case.
"The Federation reserves the right to take the appropriate measures subject to the evolution of the case."
Within Valbuena's interview with the French newspaper, the Lyon man also appeared to suggest Manchester City midfielder Samir Nasri had an involvement in the case.
However, Nasri was quick to dismiss the allegations on Friday, telling radio station RMC: "The fact that he is putting me in this situation… I will have a discussion with him.
"Honestly, I do not care about this sex-tape story. It is not my problem, not my situation.
"He is the victim, but he must not bring my name out. We are not friends. We will never be. But other people's misfortune does not make me happy."
