Post Traumatic Stress Disorder (PTSD) is heterogeneous in nature, which complicates diagnostic efforts and makes accurate assessment tools critical. The MMPI family of instruments are widely used broadband measures of psychopathology, including trauma symptomology. The MMPI-3's Anxiety Related Experiences scale (ARX) is an expansion of the MMPI-2-RF Anxiety (AXY) scale which has historically represented the MMPI family's best measure of trauma symptoms. This study expands research on ARX in 2 samples of college students (n = 332 [PCL-5 Criterion] & n = 58 [CAPS-5 Criterion]) by examining ARX's incremental, criterion, and classification validity. ARX incrementally predicted PCL-5 total and cluster scores beyond that accounted for by AXY (R2Δ = .01-.09). ARX accounted for the most unique variance, beyond RCd and RC7, in CAPS-5 interview ratings of intrusion symptoms (R2Δ = .16). ARX was strongly related to trauma symptomology broadly (r = .42-.58) and demonstrated strong screening ability at T65 (sensitivity = .37-.40; specificity = .91-.92) and stronger diagnostic screening at T75 (sensitivity = .31; specificity = .93). We discuss clinical considerations when using ARX for assessing PTSD.