Guides and Brownies will ditch the phrase "to love my God" from its Promise, instead pledging to "be true to myself and develop my beliefs."
Beginning in 1910 when the organization formed, new members were asked to "do my duty to God," and this was changed to "love my God" in 1994.
Chief Guide Gill Slocombe said the organization was aware "some people found our Promise confusing on this point and that it discouraged some girls and volunteers from joining us."
The word "country" has also been cut -- with girls asked to serve their "community" instead, but the updated Promise does retain its reference to serving Queen Elizabeth II.
"We hope that the new wording will help us reach out to girls and women who might not have considered guiding before -- so that even more girls can benefit from everything guiding can offer," Slocombe said.
Andrew Copson, chief executive of the British Humanist Association said the modified pledge made the organization "genuinely open to all, including the large number of girls and young women who don’t believe in any god."
Girlguiding is a leading UK charity for girls and young women ages 5-25, with 546,406 members.
The Girl Guide Promise now reads, "I promise that I will do my best: to be true to myself and develop my beliefs, to serve the Queen and my community, to help other people and to keep the Guide law."