Purpose: To determine the effect of family function, relationship satisfaction, and dyadic adjustment on postpartum depression. Design and Methods: This descriptive, cross-sectional study was conducted in 337 postpartum mothers. Findings: Fifty-five mothers scored above the depression scale cutoff point (>13). Emotional violence from husband, poor problem solving and communication, low relationship satisfaction, dyadic adjustment, and consensus were important risk factors for postpartum depression (p <.0.05). Practice Implications: Family function and partner relationships should be a key focus for midwives and nurses in the postpartum period. Providing psychological interventions aimed at improving relationship functioning can help protect mothers against postpartum depression.