The Canadian superstar had been rumoured to be singing a duet with Lady Gaga, but instead went solo on the Eiffel Tower to bring the four-hour event to a stirring climax.
It was Dion's first live performance in four years, and came a year and a half after she revealed a diagnosis of Stiff Person Syndrome (SPS).
SPS is a rare neurological disorder that causes muscles to spasm and can be debilitating. It also affected her distinctive, forceful voice.
Celine Dion performed on the first level of the Eiffel Tower
The 56-year-old, known as the "queen of power ballads", has been having therapy to "rebuild" her voice.
On Friday, her delivery of Edith Piaf's classic L'Hymne à l'Amour gave encouraging signs that the treatment is working.
She was accompanied by a pianist on the first level of the Eiffel Tower, beneath giant illuminated Olympic rings.
Canadian Prime Minister Justin Trudeau said that she "is a Canadian icon, an incredible talent, and she overcame a lot to be there tonight".
He added: "Celine, it’s great to see you singing again."
Italian singer Laura Pausini wrote: "My hands were shaking and my eyes were crying as I listened and saw my beloved Celine Dion."
Her appearance had been hotly anticipated, with crowds of fans waiting outside her hotel in the city in recent days.