The singer had been due to headline the West Virginia event in July (13) alongside Train, but the band cancelled its slot to take a stand against the Boy Scouts' policy which forbids openly gay or transgender candidates from joining.
Jepsen has now followed the group's lead and vowed to boycott the event unless changes are made.
In a series of posts on Twitter.com, she writes, "As an artist who believes in equality for all people, I will not be participating in the Boy Scouts of America Jamboree this summer... I always have and will continue to support the Lgbt (lesbian, gay, bisexual, and transgender) community on a global level... and stay informed on the ever changing landscape in the ongoing battle for gay rights in this country and across the globe."
Other stars who have previously urged Boy Scouts officials to reverse the policy include Neil Patrick Harris, George Takei and Ellen DeGeneres.