Sixty-one percent of the estimated 1,400 delegates of the BSA's National Council voted to end a ban that for decades has barred open homosexuality in the movement.
The resolution, passed during the gathering at the Gaylord Texan Resort & Convention Center in Grapevine, Texas, will go into force on January 1, 2014.
"The Boy Scouts of America will not sacrifice its mission, or the youth served by the movement, by allowing the organization to be consumed by a single, divisive, and unresolved societal issue," the BSA said in a statement, adding that there were no plans to further review the issue.
"While people have different opinions about this policy, we can all agree that kids are better off when they are in Scouting."
The text said "no youth may be denied membership in the Boy Scouts of America on the basis of sexual orientation or preference alone."
It updated the BSA's "membership standards," seen as symbolizing traditional US values. But the measure reaffirmed existing rules for adult Scout leaders.
The 103-year-old institution, famed for its outdoor training programs and support of wholesome virtues, has close links to the country's conservative and religious heartland.
The Boy Scouts, which is separate from the Girl Scouts of the USA, counts 2.6 million boys in its membership.
The Supreme Court ruled in 2000 in favor of the Boy Scouts, saying that the prohibition against openly homosexual members was part of its right as a private organization to free association.
Interest groups were quick to react.
"Today's vote is a significant victory for gay youth across the nation and a clear indication that the Boy Scouts' ban on gay adult leaders will also inevitably end," said Rich Ferraro with the gay rights group GLAAD.
The BSA "heard from religious leaders, corporate sponsors and so many Scouting families who want an end to discrimination against gay people, and GLAAD will continue this work with those committed to equality in Scouting until gay parents and adults are able to participate," Ferraro said in a statement.
Tony Perkins with the conservative Family Research Council vehemently disagreed with the vote result.
"Sadly, the Boy Scouts' legacy of producing great leaders has become yet another casualty of moral compromise," Perkins said in a statement. The Boy Scout delegates "succumbed to a concerted and manipulative effort by the national BSA leadership," he said.
The current BSA leadership "will bend with the winds of popular culture, and the whims of liberal special interest groups. There is little doubt that God will soon be ushered out of scouting," Perkins said.
Until there is new leadership, his group "will stand with those BSA Councils who will now act to protect boys from a new policy that only creates moral confusion and disrespects the views of the vast majority of Scouting parents," Perkins said.
A Quinnipiac University poll released in February found that voters across the country are 55 percent in favor of an end to the Scouts' ban, with only 33 percent against.