With the introduction in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) of a hybrid system of personality disorder assessment, the ability to assess patients’ traits, as well as their level of personality functioning, has become increasingly important. To assess this criterion, the DSM-5 Levels of Personality Functioning Questionnaire (DLOPFQ) was developed. The DLOPFQ assesses individuals’ self-impairments and other impairments in several domains (self-direction, identity, empathy, and intimacy) and across 2 contexts (work/school and relationships). A sample of 140 psychiatric and medical outpatients was administered the DLOPFQ and several other measures to assess its reliability and construct, incremental, and discriminant validity. The internal consistency and convergence with validation measures yielded generally meaningful and expected results. Several DLOPFQ scales and subscales were significantly correlated with measures of DSM-5 trait domains and levels of personality functioning. DLOPFQ scales also correlated with self-reported ratings of overdependence, detachment, healthy dependency, and overall mental health and well-being. The DLOPFQ also predicted interpersonal and general functioning beyond DSM-5 trait domains. These results support the reliability and validity of the DLOPFQ, which appears to be suitable for clinical use and warrants ongoing study.