Multiple Sclerosis (MS) is the most common neurodegenerative disease diagnosed in young adults. Many people live with the disease throughout their early, middle and late adulthood. It has far-reaching effects for individuals, families, and social networks. The study of its impact is an important precursor to the design of effective, efficient interventions for all concerned. This research sought to examine the physical, cognitive, and psychological effects of MS in a New Zealand community-based sample. Its impact on familial caregivers was also investigated. One hundred and two people with MS were assessed over a 14-month period. In comparisons with a demographically-matched control group, the cognitive performance of the MS sample was found to be impaired on psychometric measures of current intellectual functioning, learning, retention, delayed recall, recognition memory, and areas of attention/concentration and executive functioning. The MS sample also reported significantly more psychological difficulties than the control group. No statistically significant relationship was found between the cognitive functioning of the MS sample and their physical functioning, time since symptom onset, disease course, level of fatigue, or medication use. However, there was a statistically significant relationship between the sample’s cognitive functioning and both their psychological functioning and the time since their MS diagnosis. Analyses were undertaken with a subset of participants with MS whose cognitive performance was worse than the remainder of the MS sample in relation to the control group. This subset was found to require significantly more changes to their homes and more community services, and they experienced more social handicap than the rest of the MS sample. Familial caregivers of the participants with MS reported significantly more symptoms of anxiety and insomnia, significantly higher levels of burden, and significantly less satisfaction with the quality of social support that they received, compared to a demographically-matched control group. The caregivers’ appraisals of the functional impairments of their family members with MS made the most consistently significant unique contribution to the prediction of these areas of caregiver functioning. The significance of these results for people with MS, their familial caregivers, and society at large are discussed.