OBJECTIVE: Violence against pregnant women is a prevalent issue with severe health implications, especially during pregnancy. This study seeks to determine the prevalence of intimate partner violence against women during pregnancy and its associated mental health symptoms. DESIGN: Cross-sectional survey conducted from December 2011 to April 2012. SETTING: Muhimbili National Hospital antenatal clinic in Dar es Salaam, Tanzania. SAMPLE: 1180 pregnant antenatal care patients. METHODS: Trained interviewers conducted face-to-face standardised interviews with the women in a private room prior to their antenatal care appointment. (PTSD), anxiety and depressive symptoms were assessed through the Conflict Tactics Scale, the John Hopkins Symptom Checklist (25) and the Posttraumatic Diagnostic Scale. MAIN OUTCOME MEASURES: The Conflict Tactics Scale, the John Hopkins Symptom Checklist (25) and the Posttraumatic Diagnostic Scale. RESULTS: Of the 1180 women who were interviewed, 27% reported experiencing both physical and sexual intimate partner violence in the index pregnancy, with 18% reporting physical violence and 20% reporting sexual violence. After adjusting for the sociodemographic characteristics of women, women who experienced physical and/or sexual intimate partner violence during pregnancy were significantly more likely to have moderate PTSD (AOR 2.94, 95% CI 1.71-5.06), anxiety (AOR 3.98, 95% CI 2.85-5.57) and depressive (AOR 3.31, 95% CI 2.39-4.593) symptoms than women who did not report physical and/or sexual intimate partner violence during pregnancy. CONCLUSIONS: About three out of ten women experienced physical or sexual intimate partner violence during pregnancy by an intimate partner, which was significantly associated with poor mental health symptoms. These rates are alarming, and justify training and education of antenatal care providers to raise awareness.