Despite increased popular and research interest in youth development and outdoor education, very little research has focused upon the design principles that enhance the effectiveness of these programs. This article presents a scoping review of the literature discussing youth development activities occurring in outdoor environments, in order to identify the design principles of effective activities. This review is based upon a literature search utilising A+ Education, ERIC, PsychINFO and SPORTDiscus and sought references published between 1990 and June 2019. The literature search yielded twenty-five references that met the selection criteria established for this review. The review discerned ten design principles of effective youth development occurring in outdoor environments. A number of opportunities for further theoretical and empirical research are highlighted within the review.