"I've been working since I was eight years old... and today I am what I am," the far-right leader said during his weekly live forum on Facebook.
"Look, when a child of eight or nine years old works somewhere, many people denounce it as 'forced labour' or 'child labour,'" he said on Thursday. "But if that child smokes coca paste, nobody says anything."
"Work brings dignity to men and to women, no matter their age," he added.
He then repeated the remarks over the following days, saying at an official event on Friday that, "I worked from the age of eight planting corn, picking bananas... while studying at the same time.
"And today I am what I am. This is not demagoguery, it is the truth."
On Saturday, he republished a 2017 AFP video showing Frank Giaccio, the 11-year-old owner of a lawn mowing business and admirer of US President Donald Trump, trimming the White House lawn.
Bolsonaro added the words, "Work ennobles."
His comments provoked strongly critical reactions.
"He is the best example to incite a child not to work -- to keep him from growing up to become an adult like (Bolsonaro), with so much hatred and such incompetence," said Marcelo Freixo, a socialist politician.
Meanwhile, Brazil's media seized on a 2015 interview in which Bolsonaro's brother contradicted the head of state.
"My father had his bohemian style, but he never let one of his sons work, because he thought they had to study," Renato Bolsonaro told Crescer magazine.
Brazilian law prohibits children younger than 16 from working, except in the case of apprentices, who can begin work at 14.
According to the Brazilian Institute of Geography and Statistics (IBGE), some 2.5 million children and adolescents aged five to 17 work in Brazil.
"The argument that working would not hurt, or that it would be a viable alternative is exactly what we are fighting every day while striving to make society think differently," Patricia Sanfelici, who oversees the fight against child labour for Brazil's labour ministry, told news website UOL.
On Friday, Bolsonaro's minister for Human Rights, Family and Women, the former evangelical pastor Damares Alves, tried to put an end to the controversy.
"Our generation worked from a very young age," she said. "I worked from a very young age. But this does not mean that we are going to decriminalize (child labour).
"Let us be clear that for children to work is a violation of their rights, something that cannot be allowed."
Bolsonaro is not known for being politically correct. In 2011, he told Playboy magazine he would rather see his own son "die in an accident" than come out as gay. He has also said poor people are too ignorant to understand family planning.
And as a congressman in late 2014, he said that a colleague was not "worth raping; she is very ugly." A judge ultimately ordered him to pay the woman $2,500.
'I have been working since I was eight years old... and today I am what I am,' the far-right leader said during his weekly live forum on Facebook.