OBJECTIVE: Family and partner psychopathology characterizes 2 different types of potential risk factors for mental disorders linked to both biological and psychosocial processes, and no studies have included both variables in a study of risk of postpartum mental disorders (PPMD). The aim was to assess how a history of mental disorders in either a first-degree family member or partner affects the risk of admission or outpatient contact with PPMD. METHOD: A population-based cohort study using Danish registers was conducted, and survival analyses were performed. A total of 1,188,822 men and women became first-time parents during the study period from 1973 to 2005. The main outcome measure was incident admission or outpatient contact for any mental disorder (according to ICD-8 or ICD-10 criteria) 0 to 12 months after the birth of a first live-born child. RESULTS: A total of 2174 mothers and 1175 fathers experienced an incident admission or outpatient contact during the 12 months after the birth of the child. Mothers with no family or partner psychopathology had an increased risk of admission/outpatient contact 0 to 30 days postpartum; relative risk (RR) = 3.49 (95% CI = 3.01 to 4.04) compared to the reference group. During the same period, mothers with observed psychopathology in relatives and/or partners were at higher risk of PPMD: for family psychopathology, RR = 6.47 (95% CI = 5.25 to 7.97); for partner psychopathology, RR = 6.86 (95% CI = 3.95 to 11.90); and for both family and partner psychopathology, RR = 10.94 (95% CI = 5.18 to 23.09). Additionally, a 24-fold increased risk of PPMD 0 to 30 days postpartum was found in women with a first-degree relative with bipolar affective disorder compared to the reference group. CONCLUSION: Results indicated that family psychopathology represents a particular risk in the immediate postpartum period, especially if a family member suffers from bipolar affective disorder compared to other diagnostic groups. However, additional studies are needed to establish if partner psychopathology is a risk factor for PPMD specifically or has a more general influence on risk of mental disorders throughout pregnancy and postpartum.