Dieter Krombach was appealing the sentence by a Paris court in October 2011 which had convicted him of "deliberate violence leading to involuntary death"of his step-daughter Kalinka at their German home in 1982.
Krombach was impassive after Thursday's ruling but his lawyer, Philippe Ohayon, said he would appeal, adding that his 77-year-old client was "being sent to death row."
In a case that captivated France, Kalinka's biological father, Andre Bamberski, took the law into his own hands after Germany refused to hand Krombach over, employing a team of kidnappers to drag him to France before dumping him near a courthouse.
"I fought for this," Bamberski said after the court verdict.
Kalinka was found dead in her bed at the home she shared with her younger brother, her mother and Krombach and their two children in southern Germany in July 1982.
An autopsy proved inconclusive as to the cause of death, but forensic examinations of the body called into doubt Krombach's account of her final hours.
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A German investigation into her death found there was not enough evidence to charge Krombach but Bamberski, convinced the German had raped and killed his daughter, brought charges against him in France.
A French court in 1995 found him guilty in absentia, but Germany refused to send Krombach to France and the conviction was eventually overturned.