Objective: The purpose of this study was to validate and verify the Korean version of the Inventory of Statements about Self-Injury (ISAS) to better understand the psychopathological characteristics of nonsuicidal self-injury (NSSI) among young adults. Methods: A total of 539 Korean adults (age: 19 to 30 years; 343 participants with a history of NSSI) completed a self-report online survey regarding NSSI validation research. The test-retest reliability, internal consistency, concurrent validity, and factor analysis of the ISAS behavioral scales and the ISAS functional scales were examined. The factor structure and construct validity were evaluated by performing exploratory factor analysis (EFA) and a confirmatory factor analysis (CFA). Results: The results demonstrated the good internal consistency and temporal stability of the Korean version of the ISAS. The EFA revealed that the NSSI functions exhibited a two-factor structure: intrapersonal functions and interpersonal functions. The CFA also confirmed that the model fitness indicators of the 2-factor structure were appropriate. In addition, the ISAS functional scales were related to increased suicidal ideations and decreased resilience in participants with a history of NSSI. Conclusion: The current findings suggest that the Korean version of the ISAS is a robust measure of NSSI behaviors. Further research is needed to investigate the causal relationship between clinical symptoms, given the significant correlation between self-reported NSSI and suicidal ideation and decreased resilience.