Adolescent pregnancy, particularly unintended pregnancy, can have lasting social, economic, and health outcomes. The objective of this review is to identify high-quality interventions and evaluations to decrease unintended and repeat pregnancy among young people in low- and middle-income countries. PubMed, Embase, PsycInfo, Cinahl Plus, Popline, and the Cochrane Databases were searched for all languages for articles published through November 2015. Gray literature was searched by hand. Reference tracing was utilized, as well as unpacking systematic reviews. Selected articles were those that were evaluated as having high-quality interventions and evaluations using standardized scoring. Twenty-one high-quality interventions and evaluations were abstracted. Nine reported statistically significant declines in pregnancy rates (five cash transfer programs, one education curriculum, two life-skills curricula, and a provision of contraception intervention), seven reported increases in contraceptive use (three provision of contraception interventions, two life-skills curricula, a peer education program, and a mass media campaign), two reported decreases in sexual activity (a cash transfer program and an education and life-skills curriculum), and two reported an increase in age of sexual debut (both cash transfer programs). The selected high quality, effective interventions included in this review can inform researchers, donors, and policy makers about where to make strategic investments to decrease unintended pregnancy during young adulthood. Additionally, this review can assist with avoiding investments in interventions that failed to produce significant impact on the intended outcomes. The diversity of successful high-quality interventions, implemented in a range of venues, with a diversity of young people, suggests that there are multiple strategies that can work to prevent unintended pregnancy.