This study evaluated symptom validity scales from the Neurobehavioral Symptom Inventory (NSI) and mild Brain Injury Atypical Symptom Scale (mBIAS) in a sample of 338 combat veterans. Classification statistics were computed using the Structured Inventory of Malingered Symptomatology (SIMS) as the validity criterion. Symptom distress was assessed with the Patient Health Questionnaire-9 and Posttraumatic Stress Disorder (PTSD) Checklist-5. At SIMS > 14, the NSI total score resulted in the highest area under the curve (AUC; .91), followed by Validity-10 (AUC = .88) and mBIAS (AUC = .67). At SIMS > 23, both NSI total and Validity-10 AUCs decreased to .88; in contrast, mBIAS AUC increased to .75. The NSI total score and Validity-10 were interpreted to reflect symptom magnification, whereas the mBIAS may reflect symptom fabrication. There was a subsample with elevated Patient Health Questionnaire-9 (PHQ-9) and PTSD Checklist-5 scores who were significantly distressed but not deemed invalid on the NSI; however, there appears to be an upper threshold on the NSI total score (>69) beyond which nobody produced an invalid score on the SIMS. A recommended approach is provided for using NSI-related validity measures. (PsycInfo Database Record (c) 2021 APA, all rights reserved).