Around 100 guards walked out on Monday over a new law which forces them to become civil servants rather than be employed under the terms of their previous contracts.Talks between the guards' unions and the French ministry of culture broke down Thursday.
Management said Saturday that they had no option but to keep the museum's doors shut over the weekend when tens of thousands of visitors were expected.
The iconic gallery, which attracted 3.3 million art lovers last year, is hosting a major retrospective of the American painter Cy Twombly.
A weekend of events entitled “Imagine the France of tomorrow” was moved to another Paris venue.
Nearly 1,200 people work at the museum, which last year bucked the fall in visitor numbers of other major tourist attractions in the French capital after the Paris and Nice terror attacks.
With up to 18,000 visitors a day passing through its doors, the state-funded museum stands to lose hundreds of thousands of euros (dollars) from the stoppage.