YouthPower2: Learning and Evaluation (YP2LE) conducted a systematic review of academic and grey literature to better understand youth vulnerability and marginalization in low- and middle- income countries (LMICs); its definitions, contributing factors, youth’s experiences and access to positive youth development (PYD) programming, effective program features and scaling models, and novel dimensions of vulnerability and marginalization. The systematic review was conducted from June 2020 to December 2020. Findings and recommendations for this review are based on the examination of 118 publications, 12 key informant interviews (KIIs) and one youth focus group discussion (FGD) with four youth from USAID’s YP2LE YouthLead Network.