Partial psychiatric hospitalizations are resource-intensive clinical services designed to stabilize patients in the short term, prevent inpatient hospitalizations, and encourage long-term recovery. Typically, providers base their referral decisions on categorical diagnoses and subjective impressions of patient distress without closely considering the evidence for reporting biases. The present study followed veterans (n = 430) participating in partial psychiatric hospitalization services. We evaluated the extent to which clinical diagnoses at intake predicted treatment variables and changes in later mental health care utilization. Using hierarchical linear regressions with bootstrap confidence intervals, Minnesota Multiphasic Personality Inventory-2-Restructured Form content-based validity scales demonstrated incremental utility for predicting patient outcomes beyond intake diagnoses. Elevated Fp-r ("Infrequent Psychopathology Responses") scores independently predicted an increased number of times arriving late for partial hospitalization programming, self-report of worse current functioning at intake, and a relative increase in mental health care encounters in the 12 months following discharge. Low K-r ("Adjustment Validity") scores independently predicted self-report of worse current functioning at both intake and later discharge from partial hospitalization. Thus, indicators of severe psychopathology overreporting as well as the unlikely disavowal of emotional adjustment (i.e., high Fp-r, low K-r) predicted engagement with health care services and self-presentations of symptoms over and above the diagnostic impressions from referring providers. We discuss how indicators of content-based invalid responding on the Minnesota Multiphasic Personality Inventory-2-Restructured Form have real-world value for understanding patient behavior and shaping clinical interventions among vulnerable populations. (PsycInfo Database Record (c) 2024 APA, all rights reserved).