Objective: The Pillbox Test is a measure tapping multiple factors of executive functioning (EF) proven necessary for effective medication management. While both neurological and psychiatric presentations may include executive dysfunction, they often differ in severity. The purpose of this study is to determine whether a significant relationship exists between performance on the Pillbox Test and the primary diagnosis obtained from a neuropsychological evaluation (neurocognitive or psychiatric) in veterans. Method: Archival data was gathered from historical records obtained in a Neuropsychology Consultation Clinic at a Veterans Affairs Medical Center. Participants were 78 patients who previously completed the Pillbox Test as part of a comprehensive neuropsychological evaluation from 2011 to 2013. Data obtained included total score on the Pillbox Test, primary diagnosis obtained from a neuropsychological evaluation, and demographic variables (age, sex, education, ethnicity). No participants were excluded from the final analysis. Results: A passing score on the Pillbox Test (<5 total errors) was significantly associated with a primary psychiatric diagnosis, while a failing score (≥5 total errors) was significantly associated with a neurocognitive diagnosis, X2 (1, N = 78) = 11.5036, p < 0.0007, φ = 0.38. Conclusion: Obtaining a failing score on the Pillbox Test is associated with a neurocognitive diagnosis, while obtaining a passing score is associated with a psychiatric diagnosis. Therefore, performance on the Pillbox Test may help differentiate between primary diagnoses of neurocognitive or psychiatric origin in neuropsychological patients. Additionally, the Pillbox Test may be useful, in conjunction with other brief cognitive screeners, for identifying appropriate referrals for a comprehensive neuropsychological evaluation.