The gay marriage bill had moved through parliament successfully, and the final vote on Tuesday decided conclusively that gay marriage and gay adoption will become a reality in what has traditionally been a prominent Roman Catholic country.
President Francois Hollande, who has backed the bill, is facing stiff opposition from traditional marriage conservatives, who have taken to the streets to protest and have been engaged in a few violent clashes in recent weeks.
"We don't want your law, Hollande!" 50,000 protesters chanted on Sunday behind a banner reading: "All born of a Mum and a Dad." Opponents argue that it is undemocratic to bring about such a fundamental social change without holding a voter referendum.
"The violence comes from the way in which this was imposed," said one of the leaders of the protest, Frigide Barjot of the "A Protest for Everyone" movement, according to The Associated Press.
At the march on Sunday, many argued that legalizing same-sex marriage would be "a threat to the social fabric."
"We believe that this bill is a threat to the social fabric," said 58-year-old lawyer Patrick Poydenot. "If the bill passes, a fundamental rule of society will disappear."
While polls have shown that a narrow majority of French people do not oppose same-sex marriage, most are concerned that children and the traditional family unit may be adversely affected by the bill.
One prominent supporter of same-sex marriage, France's justice minister, Christine Taubira, has argued that allowing gay couples the right to adopt children is part of the strive for equality.
"These are children that scrape their knees, eat too much candy, don't like broccoli, drive you crazy ... we protect them," Taubira said in a statement. She added that the new law will "move our institutions towards ever more freedom, equality and personal respect."
Rural communities, meanwhile, have especially been up in arms against the bill, including conservative activists, schoolchildren with their parents, retirees and priests. One recent protest along the Champs-Elysees avenue near the presidential palace ended in blasts of tear gas and damaged cars when provincial protesters tried to charge against police in the capital.
As for Tuesday's final vote, Christophe Crepin of the police union UNSA revealed that 4,000 officers, most of them anti-riot police, had been positioned around the National Assembly building and were preparing for all possible situations.
The same-sex marriage bill is expected to be signed into law by President Hollande by the middle of the year.