Multiple Sclerosis (MS) is the most common neurological condition among young adults (aged 18-39) with approximately 100,000 people with MS (PwMS) in the UK. To counter the physical and psychological effects of living with this incurable condition, PwMS obtain assistive technology (AT) devices. These devices range from basic walking aids to complex electronic equipment, and are designed to help improve physical and psychological function. Guided by the Common Sense Model of Illness, the aim of this thesis was: (a) to establish the nature of AT use among PwMS, (b) to identify determinants of AT use, physical and psychological outcomes of MS (c) and to explore the relationship between these variables as part of self-management in MS. In order to address these objectives, a systematic review was first conducted, which identified a range of devices being utilised by PwMS with mixed effects. However many of the reviewed studies lacked theoretical insight. Determinants of AT use, and the effects of use on physical and psychological outcomes, were then explored in a qualitative focus group study. PwMS, carers and occupational therapists identified personal (e.g. illness perceptions, acceptance, optimism), device (e.g. ease of use), and external factors (e.g. AT service, social support) that may influence the uptake and continued use of AT, as well as the potential impact of using such devices (e.g. independence vs. stigma). Finally, the determinants of AT use, physical and psychological outcomes of MS were then investigated as part of a longitudinal study. PwMS were assessed at baseline and at three, six and twelve months. Physical impact of MS (baseline, 3 month), perceived illness effect (baseline, 6 month) and the psychological impact of MS (3 and 6 month) were found to be significant predictors of the physical impact of MS at 12-months. Optimism t each time point predicted 12-month psychological impact of MS. There were no significant effects of AT use on key physical or psychological variables in this study however the number of AT devices used was significantly associated with physical impact. Likelihood of AT use was increased if unemployed, or in receipt of a carer or MS medication. The findings of the presented studies have implications for future research, policy and practice around AT use and its role in self-management and self-regulation in illness.