Despite substantial problems with intimate partner violence (IPV) worldwide, the empirical support remains weak for the effectiveness of recidivism-reducing interventions for IPV perpetrators. We conducted a controlled study of the effectiveness of the Integrated Domestic Abuse Program (IDAP), a manual-based group intervention for adult male IPV offenders. A consecutive series of 340 convicted male IPV offenders who began IDAP in the Swedish Prison and Probation Services 2004 to 2007 were compared with 452 contemporary, convicted male IPV offender controls. We obtained follow-up reconviction data from the National Crime Register and used Cox regression to model the effectiveness of IDAP versus regular treatment. Treated and control subjects were all followed until March 2, 2011, for an average time-at-risk of 4.6 years (median 4.4, SD = 1.0). Twenty-five percent (n = 84) of IDAP participants recidivated in any violence versus 23% of controls (n = 104); corresponding figures for IPV specifically were 19% (n = 65) and 19% (n = 84), respectively. Intention-to-treat analyses adjusted for individual baseline risk and follow-up time suggested marginally and non-significantly lower reconviction rates in IDAP participants versus controls (hazard ratio [HR] = 0.92, 95% confidence interval [CI] = [0.69, 1.23] for any violence and HR = 0.92, 95% CI = [0.66, 1.28] for IPV, respectively). Hence, possible recidivism-reducing effects of IDAP in this cross-cultural validation were small and impossible to secure statistically. To remedy the frustrating lack of proven effective treatments for IPV offenders, better interventions should be developed and tested. Such efforts could benefit from improved knowledge about IPV-specific, causal risk factors and more powerful treatment combinations.