To examine the association between suicidal ideation (SI), 3 weeks, 3 months, and 6 months postpartum with demographic, psychosocial, clinical factors, and depressive/anxiety symptoms (measured 24-48 hours after delivery), among a cohort of postpartum women. This study included 1,073 mothers who gave birth in a large tertiary New York City hospital (2009-2010). Later, self-report SI was assessed using the suicide measure from the Edinburgh Postnatal Depression Scale and from the Patient Health Questionnaire. Two percent of participants presented with SI during the first 6 months postpartum. In bivariate analyses, race/ethnicity, nativity, insurance, and language were significantly correlated with SI 3 weeks, 3 months, and 6 months postpartum. Screening positive for depression (p = 0.0245) and anxiety (0.0454), assessed 1-2 days postpartum, was significantly correlated with later SI in bivariate analyses, as were antepartum complications (p = 0.001), depressive history (0.001), and self-efficacy (0.045). In adjusted models, antepartum complications (OR = 4.681, 95% CI = 1.99-10.99) and depressive history (OR-3.780, 95% CI = 1.514-9.441) were significantly associated with later postpartum SI. Heightened self-efficacy reduced the odds of later SI (p = 0.050). Findings suggest that SI among a relatively healthy group of new mothers occurs with some frequency. Mothers with a history of depression and antepartum complications may be at increased risk.