The 27-year-old, who was World Rugby men's 15-a-side Player of the Year in 2021, made the remark in an interview in the French LGBTQ magazine Tetu, to be published on Wednesday.
Only one professional rugby player in France, Jeremy Clamy-Edroux, who was a player at then second-tier Rouen, has publicly declared his homosexuality but Dupont said there were certainly more.
"I very much doubt that there is only one gay on the pitch!" the Toulouse and France scrum-half said.
"The goal is for all players to feel good about their sexuality and to be accepted by others."
"Even if rugby can be seen as macho, we are very open-minded, and today I think we are all capable of accepting each other's sexual orientations.
"We really need to repeat it, communicate about it, so that everyone definitely feels comfortable with it.
"Little jokes, if there is a gay person in our team and they hear them, it won't help them to speak and come out," he added.
Dupont captained France in last year's Rugby World Cup and is poised to line up for the sevens team at this summer's Games.
