Frequent relocations, disruptive separations and reunions, fragmented social support and the involvement of Service personnel in deployments are all major aspects of the military lifestyle. Despite the potential for these unique pressures to have negative influences on the mental health and well-being of spouses and partners (S/Ps) of Service personnel, there are few published studies on this population within the UK. This thesis uses both quantitative and qualitative methodologies to address the gaps in the literature by exploring the mental health and well-being of UK S/Ps. Quantitative data from 405 UK S/Ps were used to estimate the prevalence of employment, mental health, alcohol use and marital satisfaction in this population. The qualitative study explored S/Ps experiences of employment, family and social networks during accompanied postings, their relationship with the military institution and the influences on well-being. The findings suggested the mental health and well-being of S/Ps was poorer compared to women in the general population, with an increased prevalence of probable depression, hazardous alcohol consumption and a lower prevalence of relationship happiness. S/Ps described how accompanied postings restricted their sense of agency and challenged to their identity. The sense of connectedness women described with other S/Ps within the military community was described as mitigating some of these negative influences; however, women reported that such connections could be lost or weakened when they moved away from friends, other S/Ps and family, leading to isolation and disconnection. The recommendations of these findings include the provision of additional support for S/Ps to alleviate the common childcare issues women described during accompanied postings. S/Ps and their family members should be made aware of the symptoms of probable depression and hazardous alcohol use among S/Ps to improve help-seeking and additional services provided. S/Ps and Service personnel may benefit from additional relationship support.