"This is a parade that celebrates inclusion. ... That is what the city is about. That is what has made this city strong," De Blasio said after arriving at the parade, an annual tradition in Queens that attracts a few thousand participants.
In a nod to those who started the Queens parade in 2000, the mayor said it was sometimes necessary to "start a positive change, even when it doesn't seem easy."
"Over time," De Blasio added, "people cling to it. They understand it's the right way."
De Blasio also marched in the Queens parade when he was a public advocate. His predecessor, Michael Bloomberg, staunchly supported gay rights but still marched in the traditional parade for 12 years. The Manhattan parade includes about 200,000 participants and attracts more than 1 million spectators.
Irish gay advocates went to court in the early 1990s to try to win a place in the Manhattan parade where they could display their banners but judges said parade organizers had a First Amendment right to choose who participates. Since then, gay activists have protested along the route of the parade that started in 1762.
De Blasio's Irish-American police commissioner, William Bratton, has said he will march in the Manhattan parade.
In Boston, a gay equality group said Saturday that a group of gay military veterans can march under its banner as part of a tentative deal with parade organizers brokered by Boston Mayor Martin Walsh that eases a two-decade ban on gay organizations.
Walsh had threatened to boycott that city's St. Patrick's Day parade unless organizers allowed the group of gay military veterans to march.
MassEquality Executive Director Kara Coredini said that marchers from the gay-rights group would not, however, be allowed to wear clothing or hold signs that refer to sexual orientation. Negotiators will work out final details in the coming week, she said.
De Blasio urged everyone to enjoy the Queens parade and keep the new tradition alive.
"It was important to have it, to set the right tone, to set the right path for all of us," he said.