Dancers and musicians have been striking alongside public sector workers to oppose the government's plan to scrap more than 40 separate pension schemes and replace them with a single points-based system.
More than 70 shows have been cancelled since December at a loss of nearly 15 million euros ($16.5 million) — greater than the state's annual contribution to the Opera pension fund.
But on Saturday night, its Bastille venue opened its doors for the Tales of Hoffman.
“To preserve the economic integrity of the Opera, we have made the decision to go ahead with the performance this evening, but we remain mobilised for the withdrawal of this bill,” said a union representative at the start of the performance, in a statement recorded by a spectator and posted on Twitter.
It is unclear whether other planned performances will now go ahead.
The special retirement plan for the Paris Opera, which allows dancers to bow out at age 42, was introduced in 1698 by king Louis XIV — making it among the oldest in France.
The retirement age was set by taking into account the physical arduousness of the job, the high injury risk, and the assumption that most dancers cannot continue performing at their best beyond a certain age.
The French state covers half of the Paris Opera's pension fund, about 14 million euros per year.
The cancellation of several top ballet, opera, and theatre shows in Paris has disappointed tourists and locals who need to book long in advance for the pricey seats.
Dancers have staged outdoor performances in Paris in a show of support for the public sector strikes, which have triggered weeks of transport chaos