Objective: Nonsuicidal self-injury (NSSI) is prevalent among young adults and associated with negative medical and psychological consequences, necessitating its treatment. However, few treatments have been developed to treat NSSI specifically, or to treat the behavior among individuals without borderline personality disorder. The purpose of this study was to investigate the Treatment for Self-Injurious Behaviors (T-SIB), a brief, behavioral intervention specifically developed to treat NSSI among young adults, in a pilot randomized controlled trial (RCT). Method: Young adults (N = 33; age: M = 22.36 years, SD = 3.40) meeting inclusion and exclusion criteria were randomly assigned to the treatment (T-SIB; n = 15) or treatment as usual (n = 18) condition. The sample was 93.9% female, 42.4% Caucasian, and 30.3% Hispanic/Latino. Results: Feasibility and acceptability of the study and intervention were supported, and medium effects were found for decreased NSSI frequency in the T-SIB group using intent-to-treat analyses. Conclusion: Results of this study support the further evaluation of T-SIB in a larger RCT.