Non-suicidal self-injury (NSSI) is the intentional, direct destruction of one's own bodily tissue in the absence of intent to die. NSSI is both a prevalent and concerning behavior given its association with a variety of negative clinical and interpersonal outcomes. Common stereotypes and other negative beliefs about NSSI exist and may be associated with poor interpersonal functioning among those who engage in NSSI. This indicates a need to better understand the NSSI-specific stereotypes and their impact on one's self-view. Stigma, particularly self-stigma, is one potentially useful construct for characterizing this impact. A widely cited theoretical model of stigma suggests self-stigma is developed via a progressive, four-step process, and encompasses the self-application of a stereotype and its resulting harm to self-view.Despite evidence supporting the danger of self-stigma among individuals with concealable identities, research has not yet examined the impact of self-stigma specific to NSSI behavior. This may be due to a lack of a validated measure specifically measuring the construct. As such, this study sought to validate the newly developed Self-Injury Stigma Scale (SISS), a measure of NSSI stigma based on a widely used four-step model of stigma. It was hypothesized the SISS would follow a four-factor structure parallel to the four-step self-stigma process. As tests of convergent and discriminant validity, it was hypothesized measures of shame and help-seeking self-stigma would be moderately, negatively and weakly correlated, respectively, with the SISS scales. Participants from Study 1 were college students (n = 264, 65.8% female) with at least one lifetime history of NSSI. Through a series of factor analytic models, a one-factor structure of the Application of Stigma scale (i.e., third step of the four-step model) demonstrated acceptable fit and was retained as the final SISS. This factor structure was then tested on a second sample of community participants with a past-month of NSSI engagement (n = 240, 41.3% female). Confirmatory factor analysis was used to evaluate the one-factor structure and demonstrated acceptable fit on most, but not all, indices. Convergent and discriminant validity were supported, such that the final SISS scale concurrently predicted shame and help-seeking self-stigma. To examine clinical utility, relationships between the SISS and characteristics of NSSI behavior were examined, showing the SISS retrospectively predicted recent (i.e., last 3 months) frequency of NSSI, but not lifetime NSSI frequency or NSSI disclosure. As such, Study 2's hypotheses were partially supported, offering some evidence in favor of the SISS's appropriateness and utility as a measure of self-stigma of NSSI.