Mayor Bill de Blasio joined dozens of people in painting the three words with a roller on the ground Thursday morning, attracting hundreds of onlookers, reports Xinhua.
"Our city isn't just painting the words on Fifth Avenue. We're committed to the meaning of the message," he tweeted.
President Donald Trump last week lashed out at NYC plan to paint the mural, calling it "a symbol of hate" on Twitter.
In response, de Blasio said the mural is to honour members of the black community who helped build Fifth Avenue and "so much of this nation."
The mural is one of five that will be created in each borough of the city following the tragic death of African American George Floyd in Minneapolis in May, which sparked nationwide protests over racial injustice and police brutality.
"I ask all New Yorkers to recognise the power of this moment -- that the city of New York is saying loudly, clearly, consistently black lives matter and we will back up that belief with action after action after action," de Blasio said at a press briefing in mid-June while announcing the plan about the murals.