Ketamine is a dissociative anaesthetic drug which acts on the central nervous system chiefly through antagonism of the n-methyl-d-aspartate (NMDA) receptor. Recently, ketamine has attracted attention as a rapid-acting anti-depressant but other studies have also reported its efficacy in reducing problematic alcohol and drug use. This review explores the preclinical and clinical research into ketamine’s ability to treat addiction. Despite methodological limitations and the relative infancy of the field, results thus far are promising. Ketamine has been shown to effectively prolong abstinence from alcohol and heroin in detoxified alcoholics and heroin dependent individuals, respectively. Moreover, ketamine reduced craving for and self-administration of cocaine in non-treatment seeking cocaine users. However, further randomised controlled trials are urgently needed to confirm ketamine’s efficacy. Possible mechanisms by which ketamine may work within addiction include: enhancement of neuroplasticity and neurogenesis, disruption of relevant functional neural networks, treating depressive symptoms, blocking reconsolidation of drug-related memories, provoking mystical experiences and enhancing psychological therapy efficacy. Identifying the mechanisms by which ketamine exerts its therapeutic effects in addiction, from the many possible candidates, is crucial for advancing this treatment and may have broader implications understanding other psychedelic therapies. In conclusion, ketamine shows great promise as a treatment for various addictions, but well-controlled research is urgently needed. This article is part of the Special Issue entitled ‘Psychedelics: New Doors, Altered Perceptions’.