Ana Brnabic, 41, became one of the few openly gay government leaders in the world when she came to power in June, but activists say homophobia remains a widespread problem in the conservative Balkan country.
Setting off on the Pride parade with hundreds of activists waving rainbow flags and balloons, Brnabic was keen to give a more positive message, saying Serbia was "finally showing what I believe is its true face".
"We do have a very loud minority, an aggressive minority of people who are against this, but most of the people in Serbia, I think, are people who think in terms of 'live and let live'," she told AFP.
She encouraged gay youngsters to be "full of understanding for people who are very traditional and who do not yet truly understand what this is about".
In 2010, Belgrade's Pride parade descended into clashes between anti-gay protesters and police, injuring more than 100 people and prompting a three-year ban on the event.
This is the fourth consecutive year the march has gone ahead under a huge security presence, and the first time a prime minister has attended.
Serbian Prime Minister Ana Brnabic (C) attends the Belgrade Pride Parade march in Belgrade, Serbia, 17 September 2017. Source: AAP
Brnabic, who wore jeans and a dark jacket and posed for selfies with marchers, said the parade was "more relaxed" than in previous years, with a sharp reduction in police numbers.
Around 2,000 armed officers guarded the cordoned-off streets as activists marched through the city, accompanied by a soundtrack of pop music and a police helicopter buzzing overhead.
'Pinkwashing' suspicions
Brnabic was chosen for the top job by her predecessor, Aleksandar Vucic, after he was elected president. She had entered politics less than a year earlier as public administration minister.
Her appointment, endorsed by parliament, made international headlines. But sceptics suspected an attempt at "pinkwashing", with Brnabic used as a puppet by Vucic to improve Serbia's image as it campaigns to join the European Union.
Critics allege that Vucic -- still the country's most powerful politician -- is a populist authoritarian who styles himself as the only one capable of maintaining Serbian stability.
Brnabic, a technocrat with a business background, has firmly dismissed allegations that she was chosen merely because of her sexual orientation.
"I'm proud to be living in a country with a president who has actually, out of all the people, said 'I do not care whether she's gay or straight, I care whether I think she's capable'," she said on the march.
'A pragmatic person'
In a survey conducted in 2015 by the Washington-based National Democratic Institute, only 12 percent of Serbian respondents said they would completely support their child if they were homosexual.
Although the country has various legal acts addressing gender identity and anti-gay discrimination, rights activists say that implementation is poor.
They are now campaigning for the adoption of a law on same-sex partnerships, for which they hope to win the premier's support.
Asked whether she would like to see the law pass, Brnabic said: "I can't give you my personal opinion right now because I'm here as the prime minister representing the Serbian government."
There had been fears of attacks from extremists in the predominantly conservative Balkan country seeking European Union membership. Source: AAP
She said she would discuss the issue with ministers and civil society groups to "see what is it that we need to do to enable civil liberties in Serbia".
"I'm a very pragmatic person, for me it's one step at a time, and I think if we go one step at a time, that is how we build a more tolerant society."
The premier's attendance at the march drew a largely positive response from participants who spoke to AFP, although Ivana Mitrovic, a 35-year-old from the northern city of Novi Sad, was sceptical.
"I don't like the government. It's all for show," she said.
Others thought Brnabic's visibility could inspire young gay and transgender people even in traditionally-minded small villages.
"For me that's a good thing," said Nevena Pupic, 34, a rights activist and financial officer from Belgrade.
