In an interview with the French edition of Vogue for its December issue, the 44-year-old singer and supermodel said: "I'm rather in favor because I have a lot of friends - men and women - who are in this situation and I see nothing unstable or perverse in families with gay parents."
France's Socialists are pushing a bill that could see gay marriage legalized early next year. Though surveys have found that the majority of French people favor gay marriage, there has been a vocal backlash from religious leaders, voters in rural areas and ex-President Sarkozy's own UMP party.
"My husband is opposed for reasons linked to his political vocation, because he sees people as groups of thousands rather than people we know personally," she told the magazine - which featured a 20-page photo spread of her decked out in designer clothes, harking back to her supermodel days.
Bruni, no stranger to speaking her mind, also called feminism outdated - a view seemingly at odds with her image as an independent woman who forged careers in both fashion and music before settling down with Sarkozy.
"There's no need to be feminist in my generation," she said.
It's not the first time Bruni has sparked controversy on the subject. Last month, Bruni said her successor, Valerie Trierweiler, should marry her partner, President Francois Hollande, and ditch her career as a journalist.
In an interview with the French edition of Elle magazine, she dished out advice to Trierweiler, saying: "I think it is simpler to be the legitimate wife of the head of state rather than being his partner."
She added, "For my part, I felt a real easing of the general concern about me when I married Nicolas."