The weeks following the birth of a child can be stressful for new mothers. Maternal stress may be increased when mothers are dissatisfied with instrumental partner support (e.g., division of childcare duties and family decision-making power). The purpose of the current study was to determine if there is an association between dissatisfaction with partner support and maternal stress in the postpartum period, and to examine whether that association is mediated by demand-withdraw communication between partners. Participants were 49 women who completed questionnaires about satisfaction with partner support, female demand/male withdraw communication in their relationship, and their own perceived stress approximately 8 weeks after giving birth. Findings support the hypothesis that demand-withdraw communication mediates the association between dissatisfaction with partner support and maternal stress. This finding suggests that fathers' withdrawal in the context of mothers' requests for discussion or change appears to be associated with increased levels of maternal stress.