Given the diversity of individuals who undergo psychological assessment, examining whether cultural bias exists in psychological assessment instruments (i.e., differential validity) is crucial. This issue occurs when a measure systematically over- or underpredicts a criterion across demographic groups or is associated with the criterion unequally across the groups. We tested the differential validity of a widely used psychological test, the Minnesota Multiphasic Personality Inventory (MMPI)-2-Restructured Form (MMPI-2-RF), as a function of gender (male, female) and ethnicity (Caucasian, African American, and Hispanic/Latino American) in large samples of forensic psychiatric inpatients. Regression models were estimated in a multigroup framework. The analyses yielded negligible to small statistical evidence of differential validity in MMPI-2-RF scores predicting the number of future suicidal behaviors and violent behaviors in the samples. This evidence supports use of the MMPI-2-RF as a generally unbiased instrument for predicting key criteria across genders and ethnicities in a forensic psychiatric population.