A Paris court last week found Servier guilty of manslaughter and deception and imposed a fine of 2.7 million euros ($3.2 million) on the company.
The prosecutors' office said in a statement that it had appealed the court's decision to drop a charge of fraud.
Servier had no immediate comment on the appeal.
France's health ministry said that at least 500 people died of heart valve problems in the country because of exposure to the active ingredient in Mediator, which was withdrawn from sale in 2009.
(Reporting by Matthieu Protard; Editing by Alexander Smith)