For over 75 years the process of (un)forgiveness has been anecdotally understood to play an important role in the Twelve-Step Model of addiction and recovery. However, only very recently have scholars begun to examine the empirical evidence in support thereof. Multiple dimensions and aspects of forgivingness (trait), state forgiveness, and problematic substance use are relevant to one another in the context of addiction and recovery. Models of the association between forgiveness and problematic substance use have been developed, including the conceptual identification of the process of (un)forgiveness as inherent to and/or consistent with evidence-based treatment modalities. Relevant empirical evidence is reviewed and of the 21 empirical studies in the published scientific literature, 90 % show a salutary association. Indeed, forgivingness of self may be the most important dimension of forgiveness for recovery. A future research agenda is proposed and implications for individual, public, and societal health are discussed.