Objective: This study examines perinatal mental health issues, ethnic differences, and comorbidity among pregnant women in Hawaii. Methods: Eighty-four participants were recruited from women, ages 18–35, seeking prenatal care on Oahu. They were interviewed at their initial prenatal visit about substance use, depression, and anxiety. Results: Sixty-one percent of women screened positive for at least one mental health issue. Thirteen percent of all pregnant women reported drinking during pregnancy with 5% reporting problem drinking, 15% reported smoking cigarettes on a regular basis, 5% of pregnant women had probable depression, and 13% of pregnant women had probable anxiety. Significant ethnic differences were found in cigarette smoking, with the highest rate among Native Hawaiian women (35%). Native Hawaiian women were also more likely to binge drink. Conclusion: Given the high rates of potential mental health issues in our sample, our findings highlight the importance of screening and treatment for mental health issues early in pregnancy in Hawaii.