The current study sought to advance our understanding of transactional processes among maternal depression, neighborhood deprivation, and child conduct problems (CP) using two samples of low-income families assessed repeatedly from early childhood to early adolescence. After accounting for initial levels of negative parenting, independent and reciprocal effects between maternal depressive symptoms and child CP were evident across both samples, beginning in early childhood and continuing through middle childhood and adolescence. In addition, neighborhood effects were consistently found in both samples after children reached age 5, with earlier neighborhood effects on child CP and maternal depression found in the one exclusively urban sample of families with male children. The results confirm prior research on the independent contribution of maternal depression and child CP to the maintenance of both problem behaviors. The findings also have implications for designing preventative and clinical interventions to address child CP for families living in high-risk neighborhoods.