Objective This study aimed to determine the relationship between symptom self-report accuracy and objective cognitive functioning in multiple cognitive domains for varying neurocognitive impairment (NCI) subsequent to Traumatic Brain Injury (TBI). Specifically, the discrepancy between self-report and objective findings among participants with mild, moderate, and severe NCI was examined within the cognitive domains of Attention, Executive Functioning, Learning/Memory, and Speech/Language. Method The sample included archival data consisting of neuropsychological scores and self-reported Ruff Neurobehavioral Inventory (RNBI) results of 135 adult TBI patients with mild, moderate, or severe NCI who received neuropsychological assessment at a private practice. Patients were grouped based on level of impairment using Halstead Impairment Index criteria. Results No main effect was found for Attention. Patients with severe NCI had greater discrepancies in Executive Functioning (p = 0.015), Learning/Memory (p = 0.015), and Speech/Language (p < 0.001) function, when compared to those with mild NCI. Additionally, patients with severe NCI demonstrated greater discrepancies in Speech/Language (p < 0.001) function when compared to those with moderate NCI. Conclusion These findings indicate as severity of neurocognitive impairment increases for TBI patients, self-reported cognitive symptomatology—specifically executive functioning, learning/memory, and speech/language—will become less accurate. Clinically, these findings suggest that when working with patients who have severe neurocognitive deficits subsequent to TBI, it is important to consider objective testing as self-reporting may not be accurate. Understanding patient’s genuine deficits will foster patient awareness and acceptance of TBI-related cognitive deficits with increased investment in treatment and improved neurorehabilitation outcomes.