In 2008, the Minnesota Department of Corrections implemented Minnesota Circles of Support and Accountability (MnCOSA), a sex offender reentry program based on the Circles of Support and Accountability (COSA) model developed in Canada during the 1990s. Using a randomized experimental design, this study evaluates the effectiveness of MnCOSA by conducting a cost-benefit analysis and comparing recidivism outcomes in the MnCOSA (N = 31) and control groups (N = 31). Despite the small total sample size (N = 62), the results from Cox regression models suggest that MnCOSA significantly reduced three of the five recidivism measures examined. By the end of 2011, none of the MnCOSA offenders had been rearrested for a new sex offense compared with one offender in the control group. Because of less recidivism observed among MnCOSA participants, the results from the cost-benefit analysis show the program has produced an estimated US$363,211 in costs avoided to the state, resulting in a benefit of US$11,716 per participant. For every dollar spent on MnCOSA, the program has generated an estimated benefit of US$1.82 (an 82% return on investment). (Author's abstract)