Our aim was to investigate serum brain-derived neurotrophic factor (BDNF) levels in postpartum women, according to the presence of postpartum affective disorder (PPAD) and suicidality. A cross-sectional study was carried out with women between 45 and 90 days after delivery. PPAD (depression, manic and mixed episode) and suicide risk were assessed using the Mini International Neuropsychiatric Interview. BDNF was assessed using a commercial ELISA kit. Linear regression was used for multivariate analyses. A hundred ninety women participated in the study, 15.3 % had PPAD, 7.4 % showed PPAD with suicide risk. BDNF levels were lower in subjects with three or more Stressful Life Events (P = 0.01). The serum BDNF levels of women with PPAD presenting suicide risk were significantly lower than those of women without suicide risk (1.50 ± 1.38 and 2.33 ± 1.28 ng/ml, P = 0.02). Clinicians should enquire postpartum women about their history of stressful life events, PPAD, and suicidality. This study shows the potential role of BDNF in the neurobiology of the association of PPAD and suicidality.