Prenatal stress can have a lasting effect on women's mental health after childbirth. The negative effects may be particularly salient in women from low income and ethnic minority backgrounds, who are at increased risk for postpartum depression. However, social support may have the potential to attenuate the negative impact of stress. The present study evaluated 269 Mexican American women (ages 18-42; 83 % Spanish-speaking; median income $10,000-$15,000) for prenatal stress (daily hassles, family stress, partner stress, and culture-specific stress) in relation to depressive symptoms 6 weeks postpartum. Prenatal social support was examined as a buffer against the impact of prenatal stress. Partner stress, family stress, and daily hassles uniquely predicted depressive symptoms. Moderate and high levels of social support attenuated risk for depression due to family stressors. Prenatal interpersonal and daily stressors negatively impact the mental health of women after birth, but social support can mitigate some of these effects. Among Mexican American pregnant women, effective interpersonal support and stress management may be associated with reduced risk for postpartum depression.