The walkout comes as the museum is still reeling from the brazen theft in October of jewels worth 88 million euros ($A156 million) and recent infrastructure problems including a water leak that damaged ancient books.
The Louvre normally welcomes approximately 30,000 visitors daily.
Because the museum is routinely closed on Tuesday, it will not re-open before Wednesday when workers will have to decide whether the strike continues.
After unions warned of a strike last week, the museum remained shut at the usual opening time of 9am on Monday, shortly before a vote confirming the walkout.
About 400 out of the museum's 2200 employees supported the labour action.
"Due to a strike, the museum is closed for the day," the Louvre said on X.
The strike, called by the CFDT, CGT and Sud unions, follows what they described as "increasingly degraded working conditions" and insufficient staffing.
The unions said employees were suffering from "an ever-increasing workload" and "contradictory instructions" that prevented them from carrying out their duties properly.
Union requests include hiring more permanent staff, particularly in security and visitor services, and improved working conditions.
The unions also oppose a 45 per cent ticket price increase from mid-January for non-European Union tourists.
The hike is meant to help finance renovations.
"We know very well that visiting the Louvre is sometimes the trip of a lifetime. So we really don't want to penalise visitors," Elise Muller, national secretary of Sud Culture union, told Reuters.
"In fact, we feel like we're the last ones trying to insist that the public should be able to visit a Louvre that is safe, a Louvre that has been neglected by its management for several years now."
Some tourists came to the Louvre early on Monday despite the threatened strike, and found it shut.
"We get here and we see them taking the placards that say the time and turning them around, and one of them said the Louvre is closed," US visitor Gretchen Johnson said.
"And so then we went up and asked: 'when will it open?' He said: 'probably not this morning, for sure not this morning'."
Melissa Frisvold, also from the US, said: "As tourists we do not want to interfere in your politics. We just want to be gracious. So we understand when people need to go on strike."
