Despite the contribution of mental ill-health to perinatal morbidity and mortality, the experiences of adolescent girls and young women (AGYW) in low- and middle-income countries remain overlooked. This review explores potential intersecting vulnerabilities for perinatal mental health to identify the prevalence, risk factors, interventions, and implications for health services and future research. We searched mixed-methods English-language studies in four databases (MEDLINE, PsycInfo, Global Health, Embase) published between January 1, 2000 and April 30, 2022 reporting age-disaggregated data on the prevalence, risk factors, and interventions for AGYW's mental health during pregnancy through one year postpartum (quantitative) and/or the mental health experiences of AGYW in the perinatal period (qualitative). Our search yielded 3205 results, of which 48 met the inclusion criteria. Both regions observe a paucity of robust evidence and intervention evaluations, particularly South Asia. While meta-analysis was infeasible due to study heterogeneity, quantitative studies do identify individual-level risk factors for perinatal depression. Qualitative studies emphasise stigma's impact, among other societal-level social risk factors, on diverse perinatal mental health outcomes of importance to AGYW themselves. Rigorous evaluations of interventions are lacking bar two protocols with forthcoming results. Evidence gaps persist concerning prevalence of outcomes beyond depression and implications of AGYW's perinatal experiences including pregnancy/perinatal loss and obstetric and postpartum complications. High-quality research, including comparable prevalence and multi-method evidence identifying risk and protective factors and promising interventions is urgently needed to improve adolescent wellbeing in the perinatal period. A key strength of this review is our assessment of available evidence for both regions. In doing so, we address a critical blind spot of prior reviews that focused either on adult perinatal mental health in low- and middle-income countries, or on AGYW perinatal mental health in high-income settings but neglected the intersection of these potential vulnerabilities for these high-burden, low-resource contexts.