This study examined the classification accuracy of the WMS-III primary indices in the detection of Malingered Neurocognitive Dysfunction (MND) in Traumatic Brain Injury (TBI) using a known-groups design. Sensitivity, specificity, and positive predictive power are presented for a range of index scores comparing mild TBI non-malingering (n = 34) and mild TBI malingering (n = 31) groups. A moderate/severe TBI non-malingering (n = 28) and general clinical group (n = 93) are presented to examine specificity in these samples. In mild TBI, sensitivities for the primary indices ranged from 26% to 68% at 97% specificity. Three systems used to combine all eight index scores were also examined and all achieved at least 58% sensitivity at 97% specificity in mild TBI. Specificity was generally lower in the moderate/severe TBI and clinical comparison groups. This study indicates that the WMS-III primary indices can accurately identify malingered neurocognitive dysfunction in mild TBI when used as part of a comprehensive classification system.