The parade Saturday went from Montparnasse to Bastille, Radio France Internationale reported.
Organizers said attendance was up from last year's estimated 36,000 people, and local gay rights activist Valerie Perrin said she believes more people will come in following years if gay marriage is legalized.
"The law is not yet voted ... [but] I think next year it will be a big, big, big party!" she said.
Prime Minister Jean-Marc Ayrault said Friday the right to marriage, as well as adoption, would be open to "everyone," without giving a specific date for when that would happen.