Objectives: This study examined predictive associations of substance abuse with treatment engagement variables and partner abuse outcomes and explored the extent to which treatment engagement and ongoing alcohol consumption mediated the association between pretreatment substance use and posttreatment abuse. Method: Data were collected from 145 partner abusive men in treatment and partners using standardized measures of violence, alcohol and drug use at baseline, posttreatment, and follow-up assessments. Results: Men who screened positive for alcohol or drug problems at baseline had significantly lower treatment engagement and higher self-reports of partner abuse before and during treatment. Partial support was found for the mediation model. Conclusions: The implications for social work practitioners who work in interdisciplinary settings with intimate partner violence perpetrators and survivors are discussed. (Contains 6 tables.)