This study describes the utilization of health care services related to psychiatric diagnoses in an inner city community health organization with a largely Hispanic population of low socioeconomic status. We reviewed the frequency and timing of postpartum mental health diagnoses among 5,731 patients who delivered babies and were followed-up for postpartum care. 286 women (5 %) had at least one mental health diagnosis. The rates in white, black, and Hispanic women were 12, 8, and 5 % respectively (p < .05). White and black women were 2.5 (95 % CI 1.24, 5.07), and 1.62 (95 % CI 1.09, 2.40) times more likely to have a mental health diagnosis, respectively, compared to Hispanic women. The most common diagnoses were mood disorders (64 %) followed by anxiety disorders (29 %). 87 % of cases were diagnosed after 4 weeks postpartum. The postpartum mental health diagnosis rate seen here is lower than might be expected, particularly among Hispanic women. Possible explanations are discussed.