Applied psychologists commonly use personality tests in employee selection systems because of their advantages regarding incremental criterion-related validity and less adverse impact relative to cognitive ability tests. Although personality tests have seen limited legal challenges in the past, we posit that the use of personality tests might see increased challenges under the Americans with Disabilities Act (ADA) and the ADA Amendments Act (ADAAA) due to emerging evidence that normative personality and personality disorders belong to common continua. This article aims to begin a discussion and offer initial insight regarding the possible implications of this research for personality testing under the ADA. We review past case law, scholarship in employment law, Equal Employment Opportunity Commission (EEOC) guidance regarding “medical examinations,” and recent literature from various psychology disciplines—including clinical, neuropsychology, and applied personality psychology—regarding the relationship between normative personality and personality disorders. More importantly, we review suggestions proposing the five-factor model (FFM) be used to diagnose personality disorders (PDs) and recent changes in the Diagnostic and Statistical Manual of Mental Disorders (DSM). Our review suggests that as scientific understanding of personality progresses, practitioners will need to exercise evermore caution when choosing personality measures for use in selection systems. We conclude with six recommendations for applied psychologists when developing or choosing personality measures.