Background: Unintended pregnancy among adolescents represents an important public health challenge in high-income countries, as well as middle and low-income countries. Numerous prevention strategies such as health education, skills-building and improving accessibility to contraceptives have been employed by countries across the world, in an effort to address this problem. However, there is uncertainty regarding the effects of these interventions, hence the need to review the evidence-base. Objectives: To assess the effects of primary prevention interventions (school-based, community/home-based, clinic-based, and faith-based) on unintended pregnancies among adolescents.