Pascal Simbikangwa, 58, was sentenced to 25 years in 2014 in a trial that marked a turning point in France's approach to genocide suspects living on its soil.
The former presidential guard member had already lost an appeal against his conviction for crimes against humanity and genocide in 2016.
The Cour de Cassation, France's court of final appeal, on Thursday ruled it was "obvious" that Simbikangwa had "willingly participated in abuses against the Tutsis and against the civilian population in general".
Simbikangwa, who has been confined to a wheelchair since a car crash in the 1980s, was accused of organising roadblocks where Hutu militia carried out murders, mainly targeting the Tutsi minority. He always insisted his innocence.
More than 800,000 people died during the Rwanda genocide, mostly ethnic Tutsis as well as some moderate Hutus.
The three-month slaughter began after the plane of then president Juvenal Habyarimana, a Hutu, was shot down in April 1994.
In a separate case, prosecutors in Paris asked judges to order a Rwandan former doctor accused of being an accomplice in the genocide to stand trial in a criminal court, following an investigation that began 23 years ago.
Tense relations
Prosecutors accuse Sosthenes Munyemana, who fled to France after the end of the massacre, of signing a "motion of support" for government genocide and detaining Tutsi civilians under inhumane conditions.
His lawyer, Jean-Yves Dupeux, said the former gynaecologist had "behaved as he should have in trying to protect refugees in a difficult situation".
Meanwhile, other cases in France involving Rwandans accused of committing atrocities in the genocide are also being appealed.
Former eastern Rwandan mayors Octavien Ngenzi and Tito Barahira -- prosecuted over the genocide -- are both appealing life sentences they were handed in 2016.
The two were convicted of crimes against humanity and genocide over the "massive and systematic summary executions" of Tutsis in Kabarondo in 1994.
For decades, the genocide has led to tensions between France and the small East African country.
Rwanda has accused France of complicity in the mass killings through its support of ethnic Hutu forces who carried out most of the slaughter.
France has admitted it made mistakes but insists it never had a role in the massacre. It had previously also been accused of dragging its feet over prosecuting cases.
After meeting Rwandan President Paul Kagame in Paris, French President Emmanuel Macron on Wednesday backed a Rwandan candidate to head the world association of French-speaking nations, in a move likely to strengthen France's ties with Rwanda.
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