Giant heart, flags and umbrellas in the colors of the rainbow, the event took place legally along the Danube in scorching heat.
The participants, including foreign diplomats, condemned the text adopted in the summer of 2021 which prohibits "the representation or promotion" of homosexuality and sex change among minors.
"It's a tool to divide people and pit them against each other," according to marketing expert Armin, who declined to give his last name.
"To be frank, the situation is depressing," said Pal Vas, an 18-year-old student who will leave Hungary in September for his studies.
"I'm lucky to have an open family and friends, but I know so many LGBT people who are forced to hide," says the young man, who recounts having recently been insulted in the street. "Just because I was wearing a pink t-shirt".
Annamaria Nemet, a 54-year-old saleswoman, came in solidarity with her son. "I cannot accept the fact that he is considered a second-class citizen in his own country," she said. "We are a retrograde society".
On a bridge in the city, counter-demonstrators had unfurled a banner confusing homosexuality and pedophilia, like the law.
The Hungarian law, originally aimed at combating pedocrime, raised an outcry in Europe last year: Commission President Ursula von der Leyen spoke of "shame". In the process, the European executive had launched an infringement procedure against Hungary, before seizing the Court of Justice of the EU in mid-July.
Nationalist and ultra-conservative Prime Minister Viktor Orban, whose country is in the crosshairs of Brussels for its attacks on the rule of law, assures that the law is not homophobic and aims to "protect the rights of children".
On Saturday, during a speech in Romania, he reaffirmed the government's position: "The father is a man, the mother is a woman, leave our children alone", he insisted, rejecting "the Western nonsense" on the subject.
