The objective of this study was to test whether partner communication about HIV and/or alcohol intoxication mediated reductions in intimate partner violence (IPV) in SEPA (Salud [health], Educación [education], Promoción [promotion], y [and] Autocuidado [self-care]), a culturally specific, theoretically based group HIV-risk reduction intervention for Hispanic women. SEPA had five sessions covering sexually transmitted infection (STI)/HIV prevention, partner communication, condom negotiation and use, and IPV. SEPA reduced IPV and alcohol intoxication, and improved partner communication compared with controls in a randomized trial with adult U.S. Hispanic women (SEPA, n = 274; delayed intervention control, n = 274) who completed structured interviews at baseline and 3, 6, and 12 months post-baseline. Parallel process latent growth curve models indicated that partner communication about HIV mediated the reduction in male-to-female IPV in SEPA, B = -0.78, SE = 0.14, p< .001, but alcohol intoxication did not, B = -0.15, SE = 0.19, p = .431. Male-to-female IPV mediated the intervention effect on female-to-male IPV, B = -1.21, SE = 0.24, p< .001. Skills building strategies originally designed to enhance women's communication with their partners about sexual risk behaviors also worked to reduce male-to-female IPV, which in turn reduced female-to-male IPV. These strategies could be integrated into other types of health promotion interventions.