Objectives: The main aim of the present study was to confirm the two‐factor structure of the Inventory of Statements About Self‐injury‐ Part II (ISAS‐II), analyze its psychometric properties and test-retest reliability of Parts I and II of the ISAS. Method: The sample was composed of 355 Spanish participants diagnosed with eating disorders or borderline personality disorder (mean age 27.89, standard deviation = 13.31; 315 women, 40 men). Two models proposed for the ISAS‐II were analyzed by means of confirmatory factorial analysis. Results: A two‐factor model was confirmed, and a model with self‐care included in the intrapersonal factor was preferable. The ISAS‐II showed positive correlations with emotional dysregulation. Test-retest reliability showed statistically significant correlations at 7 months (n = 123). Conclusion: The ISAS‐II is a valid instrument to assess nonsuicidal self‐injury in Spanish populations, making it possible to assess these behaviors, which require valid and reliable measures worldwide.