The Boy Scouts of America said its membership fell by 6 percent last year.
The news comes after the Scouts' leadership voted last May to allow openly gay young people join.
That change made many volunteers from churches angry since they consider homosexuality a sin and a violation of the values of Scouting.
The Southern Baptist Convention also disagreed with the move. The group left it up to individual churches to decide if they want to stay with the Scouts.
Some who left went to a group called Trail Life USA, an organization set up by conservatives and Christian groups.