Activists dressed in black with "no to racism" on their sweaters were reportedly beaten up by attendees and hauled out of the room the event was taking place by security guards.
Mr Zemmour, a former French TV pundit, formally declared his candidacy in a video last week which highlighted his anti-migrant and anti-Islam views.
“We must give back the power to the people, take it back from minorities that oppress the majority,” he said, over footage of women wearing headscarves and Black men on trains.
The presidential candidate went on trial in Paris earlier this month on charges relating to inciting racial hatred after he called unaccompanied child migrants “thieves, killers and rapists”. He was previously convicted of hate speech after justifying discrimination against Black and Arab people in 2010, and of incitement to religious hatred for anti-Islam comments in 2016.
Thousands of people took to the streets of Paris in protest as he launched his campaign on Sunday.
At the rally, reporters from the Associated Press reported seeing anti-racist activists being beaten up by attendees and brutally taken out of the room.
The scuffles continued outside the room between anti-racism activists and security guards.
Meanwhile, his supporters sang France’s national anthem, shouted "Zemmour, president!" and "We will win!" while brandishing the tricolor French flag.
"I’m not racist," Mr Zemmour insisted. "We are defending our country, our homeland, our ancestral heritage [to] ... transmit our children to France as we have known it."
Following a commotion involving journalists, he later added: “My adversaries want my political death, journalists want my social death and jihadists want my death.”
Mr Zemmour has said he wants foreigners to "assimilate” to French culture a ban on parents from giving children “foreign” names instead of traditional French names.
He also wants to end nationality being acquired by birth on French soil and to deport foreign criminals and foreign jobseekers who do not find employment within six months.
"France is back, because the French people stood up. The French people stand up against those who want to make it disappear," he said.
France is holding its presidential election on 10 April, with a runoff if needed on 24 April.
Mr Zemmour has drawn comparisons in France to former US president Donald Trump because of his rabble-rousing populism and ambitions of making the jump from the small screen to national leadership.
The 63-year-old unveiled his campaign’s slogan “Impossible is not French," a quote attributed to Napoleon.
His opponents include Valerie Pecresse, the head of the Paris region and a former minister from 2007 to 2012, who is the presidential candidate for France’s main conservative Republicans party, and the far-left leader of the Rebel France party, Jean-Luc Melenchon, who is seeking the presidency for the third time.
Other presidential candidates on the left include Paris Mayor Anne Hidalgo for the Socialist party and Yannick Jadot, a former Greenpeace activist, for the Greens.
Mr Zemmour is siphoning off supporters from far-right National Party leader Marine Le Pen, who has long said she would run for the French presidency next year.
French President Emmanuel Macron, who defeated Le Pen in the 2017 presidential runoff, is expected to seek a second term but has yet to declare his candidacy.
Pauline Salingue, a spokeswoman for the head of the New Anti-Capitalist Party, said people "shouldn’t be seduced by these so-called anti-system profiles.
“Zemmour is a multi-millionaire,” she added. “Zemmour earns tens of thousands of euros per month, so how can he pretend to represent the little people, as he likes to say? It is a very serious scam."
Additional reporting by AP
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