Mandating offenders to attend correctional treatment is a controversial function of the justice system, in part because of the uncertainty about the effectiveness of such practice. A meta-analysis was conducted to compare the effectiveness of mandated, coerced, and voluntary correctional treatment in reducing recidivism. A search of correctional treatment studies resulted in 129 studies meeting the inclusion criteria. In general, mandated treatment was found to be ineffective in several analyses, particularly when the treatment was located in custodial settings, whereas voluntary treatment produced significant treatment effect sizes regardless of setting. Few significant differences in effect sizes were found between levels of coercion. The implications of mandating correctional treatment for offenders are discussed.