Recent models of impaired awareness in brain injury draw a distinction between metacognitive knowledge of difficulties and online awareness of errors (emergent and anticipatory). We examined performance of 31 Traumatic Brain Injury (TBI) participants and 31 healthy controls using a three-strand approach to assessing awareness. Metacognitive knowledge was assessed with an awareness interview and discrepancy scores on three questionnaires--Patient Competency Rating Scale, Frontal Systems Behavioral Scale and the Cognitive Failures Questionnaire. Online Emergent Awareness was assessed using an online error-monitoring task while participants performed tasks of sustained attention. Online anticipatory awareness was examined using prediction performance on two cognitive tasks. Results indicated that the TBI Low Self-Awareness (SA) group and High SA group did not differ in terms of severity, chronicity or standard neuropsychological tasks but those with Low SA were more likely to exhibit disinhibition, interpersonal problems and more difficulties in total competency. Sustained attention abilities were associated with both types of online awareness (emergent and anticipatory). There was a strong relationship between online emergent and online anticipatory awareness. Metacognitive knowledge did not correlate with the other two measures. This study highlights the necessity in adopting a multidimensional approach to assessing the multifaceted phenomenon of awareness of deficits.