Restorative justice has increased in popularity as a response to crime that may prevent some of the counterproductive outcomes of conventional criminal justice and juvenile justice practices. Restorative justice may more effectively involve and respond to the needs of victims than conventional criminal justice and juvenile justice, and may confer benefits to offenders and communities. Despite increased interest from government actors and members of the public, there are no established evidence-based restorative justice practices. Significant gaps in knowledge remain in terms of program development, facilitator training, and program implementation, which undoubtedly contribute to the varied participant outcomes observed in the literature. These gaps in knowledge are attributable to the reliance on theoretical models of restorative justice and outcomes evaluations, without sufficient research examining the mechanisms that produce positive or negative outcomes for participants. This uncracked black box of restorative justice inhibits the identification of restorative practices that are beneficial to victims, offenders, and other affected parties across offense types.