Objective: To empirically-derive a new MMPI-2 sub-scale, the 13-item Cognitive Complaints Scale (CCS), as an embedded measure of symptom validity. This study hypothesized that mild traumatic brain injured subjects with financial incentives who failed performance validity tests (PVTs) would score significantly higher on the CCS compared to mild traumatic brain injured subjects with financial incentives who passed PVTs. Mild traumatic brain injured controls with no financial incentives were predicted to score lowest on the CCS. Research design: A known groups design was utilized as this design allows for the accurate classification of criterion groups. Methods: One hundred and fifty mild head-injured adults were assigned to one of three groups: the Failed Performance Validity (FPV) group, the Passed Performance Validity (PPV) group or a control group. Results: An ANOVA revealed that the FPV group scored significantly higher on the CCS compared to the PPV group. Controls with no financial incentives scored lowest. A CCS cut-score of 12 discriminated between the FPV and PPV groups at a high level of specificity (94%). Conclusions: A dissociation between 'performance validity' and 'symptom validity' supports recommendations for the differential application of these descriptive terms. The CCS may be helpful to assess credibility of clinical presentation in situations where PVTs are absent. © 2014 Informa UK Ltd.