This study examined whether posttraumatic stress specifically resulting from intimate partner violence (IPV-related posttraumatic stress) mediated relationships between types of IPV and drug and alcohol problems among 212 women currently experiencing IPV. Six-month prevalence was high for drug use (48%) and alcohol use (59%). Structural equation modeling revealed that the frequency of physical, sexual, and psychological IPV were significantly and positively related to greater IPV-related posttraumatic stress, and IPV-related posttraumatic stress was significantly and positively related to drug problems. Further, IPV-related posttraumatic stress mediated the relationships between physical IPV and drug problems and psychological IPV and drug problems. Findings suggest that prevention and intervention efforts targeting posttraumatic stress among IPV-exposed women may reduce drug problems in this population.