Postpartum depression (PPD) is a major mental health disorder that affects at least 13 percent of new mothers and has detrimental consequences for populations that are of concern to social workers, such as low-income women, women of color, young women, and single mothers. Despite the relevance of PPD to multiple social work problems and populations, the social work literature contains sparse information about the causes of, consequences of, and treatments for PPD among vulnerable groups of new mothers. In this article, the authors review the literature on PPD with specific attention to the sociocultural dimensions of the disorder, barriers to treatment, and the relationship of PPD to social work theory and practice. The authors argue that social workers should set an agenda for PPD research that draws on the profession's biopsychosocial perspective, advances a culturally competent understanding of the experience of PPD, and informs social work practice with diverse groups of new mothers.