This thesis aimed to explore the role of self-efficacy in Multiple Sclerosis. The thesis begins with a systematic literature review and meta-analysis to examine whether fatigue management interventions, based upon energy conservation strategies, increase selfefficacy in people with Multiple Sclerosis experiencing fatigue. Three databases were searched, and a total of nine articles were identified as meeting the inclusion criteria. Meta-analysis revealed a medium effect of energy conservation nterventions in reducing fatigue, and a large effect of energy conservation interventions in increasing self-efficacy. The findings from this systematic review suggest that energy conservation interventions are effective at increasing self-efficacy in people with Multiple Sclerosis, as well as reducing the impact of fatigue. The literature review is followed by an empirical paper, which aimed to investigate whether self-efficacy remains predictive of perceived cognitive impairment after controlling for objective cognitive functioning. This empirical paper also aimed to further explore the relationship between self-efficacy and cognitive domains (i.e., attention, processing speed, memory, and executive functioning), as measured objectively. A convenience sample of 25 adults with Multiple Sclerosis was recruited from a semi-rural part of North Wales. All participants completed a series of questionnaires and undertook a battery of neuropsychological assessments. Using hierarchical regression analyses, selfefficacy was found to significantly predict perceived cognitive impairment, even after controlling for objective cognitive functioning. Correlational analyses also revealed a significant relationship between self-efficacy and processing speed, and self-efficacy and executive function. The paper concludes that self-efficacy is associated with perceived cognitive impairment in people with Multiple Sclerosis, and therefore may be an important aspect of self-management programmes. The third chapter of this thesis addresses the implications for theory development and clinical practice, and future research. A reflective commentary is also enclosed.