Postpartum depression (PPD) is a debilitating illness with negative consequences for affected mothers and their children (e.g., poor maternal-infant attachment, deficits in children's social, emotional, and cognitive development). While it is suggested that adolescent mothers are at increased risk of PPD, there is a paucity of research exploring factors that place adolescent mothers at risk. This systematic review aims to identify risk factors associated with adolescent PPD and appraise the quality of this evidence-base. A systematic review was conducted in May of 2018, using PsycINFO, EMBASE, MEDLINE, ASSIA, CINAHL, MIDIRS, and ProQuest Dissertations and Theses Global database, following PRISMA guidelines. Inclusion criteria included studies from developed countries; published after 1992; using a validated measure of PPD; with onset of illness within 12 months of childbirth, but which had persisted past two-weeks postpartum; adolescent mothers < 20 years of age; and risk factor(s) that occurred prior to birth. Fourteen studies were included, ranging from weak-to-strong in quality. Results suggest several risk factors implicated in the onset of adolescent PPD, including prior depression, lack of familial social support, and socio-economic hardship. Awareness of risk factors for healthcare professionals working with pregnant adolescents is of high importance to better facilitate early identification and to provide support for adolescents at risk. Future research ought to consider employing prospective longitudinal designs, along with clearly defined, timely and validated measurements of risk factors and PPD. Limitations include only studies published in English and low agreement on the included studies selection bias.