The Boy Scouts of America's National Council has voted to ease a long-standing ban and allow openly gay boys to be accepted as Scouts.
60% of the local scout leaders voted to support the proposal.
Under the proposal drafted by the scouts' governing board, gay adults will remain barred from serving as scout leaders.
The outcome is unlikely to end a bitter debate over the scouts' membership policy.
Some conservative churches that sponsor scout units wanted to continue excluding gay youths, in some cases threatening to defect if the ban were lifted.
More liberal scout leaders while supporting the proposal to accept gay youth have made clear they want the ban on gay adults lifted as well.
Many scout units in conservative areas feared their local donors would stop giving if the ban on gay youth were lifted, while many major corporate donors were likely to withhold donations if the ban had remained.
In January, the BSA executive committee suggested a plan to give sponsors of local scout units the option of admitting gays as both youth members and adult leaders or continuing to exclude them.
However, the plan won little praise, and the BSA changed course after assessing responses to surveys sent out starting in February to members of the scouting community.
The BSA's overall "traditional youth membership" - Cub Scouts, Boy Scouts and Venturers - is now about 2.6 million, compared with more than 4 million in peak years of the past.
The organisation, which celebrated its 100th anniversary in 2010, has long excluded both gays and atheists.
Protests over the no-gays policy gained momentum in 2000, when the US Supreme Court upheld the BSA's right to exclude gays.
Scout units lost sponsorships by public schools and other entities that adhered to non-discrimination policies, and several local scout councils made public their displeasure with the policy.
