Objective: To empirically evaluate the diagnostic relevance of the proposed Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM–5; APA, 2013) Criterion-A frequency threshold for nonsuicidal self-injury (NSSI) disorder. Method: Archival, de-identified, self-reported clinical assessment data from 746 adolescent psychiatric patients (Mage = 14.97; 88% female; 76% White) were used. The sample was randomly split into 2 unique samples for data analyses. Measures included assessments of NSSI, proposed DSM–5 NSSI-disorder criteria, psychopathology, dysfunction, distress, functional impairment, and suicidality. Results: Discriminant-function analyses run with Sample A identified a significant differentiation of groups based on a frequency of NSSI at 25 or more days in the past year, Λ = .814, χ2(54) = 72.59, p < .05, canonical R2 = .36. This cutoff was replicated in the second sample. All patients were coded into 1 of 3 empirically derived NSSI-frequency cutoff groups: high (>25 days), moderate (5–24 days), and low (1–4 days) and compared. The high-NSSI group scored higher on most NSSI features, including DSM–5-proposed Criterion-B and -C symptoms, depression, psychotic symptoms, substance abuse, borderline personality-disorder features, suicidal ideation, and suicide plans, than the moderate- and low-NSSI groups, who did not differ from each other on many of the variables. Conclusion: The currently proposed DSM–5 Criterion-A frequency threshold for NSSI disorder lacks validity and clinical utility. The field needs to consider raising the frequency threshold to ensure that a meaningful and valid set of diagnostic criteria are established, and to avoid overpathologizing individuals who infrequently engage in NSSI.