Social support is an important determinant of adjustment following traumatic brain injury (TBI) sustained by a family member. The present study examined the extent to which social support moderates the influence of characteristics of the person with injury on caregiver subjective well-being. Sixty pairs of individuals who had sustained a moderate to severe TBI and their caregivers (N=120) participated. Years postinjury ranged from 0.3 to 9.9 ( M=4.8, SD=2.6). Cognitive, functional, and neurobehavioral functioning of participants with TBI were assessed using neuropsychological tests and rating scales. Caregiver life satisfaction and perceived social support were assessed using self-report questionnaires. Results indicated that time since injury was unrelated to life satisfaction. Neurobehavioral disturbances showed an inverse relation with life satisfaction. Social support emerged as an important moderator of life satisfaction. Only among caregivers with low social support was cognitive dysfunction adversely related to life satisfaction. Similarly, a trend suggested that patient unawareness of deficit was associated with caregiver life dissatisfaction only among caregivers with low social support. In contrast, these characteristics were unrelated to life satisfaction among caregivers with adequate social support.