Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disorder of the central nervous system with common symptoms of rapid onset of eye pain, loss of vision, neck/back pain, paralysis, bowel and bladder dysfunction and heat sensitivity. The rare, unpredictable, and debilitating nature of NMOSD constitutes a unique psychological burden for patients and their caregivers, the specific nature and extent of which is not yet known. This mixed methods study, informed by both quantitative and qualitative data collected via self-report measures, focus groups, and in-depth interviews, aims to investigate and understand the psychological burden of patients with NMOSD and their caregiver/loved ones, so as to inform a specialized intervention. 31 adults living with NMOSD and 22 caregivers of people with NMOSD in the United States and Canada, recruited from NMOSD patient advocacy groups, social media groups, and through word of mouth from other participants, completed a battery of standardized self-report measures of anxiety, depression, trauma, cognitive fusion, valued living, and coping styles. Semi-structured focus group sessions were conducted via HIPAA-compliant Zoom with 31 patients, and separate focus groups were conducted with 22 caregivers. A subset of these samples, comprised of 16 patients and 11 caregivers, participated in individual semi-structured interviews, prioritizing inclusion of diverse perspectives. Descriptive statistics and bivariate correlations were run on quantitative self-report data using SPSS [Version 28.0.1]; data were stored in REDCap. Reflexive thematic analysis was employed regarding qualitative individual interview data. The majority of patients reported experiencing anxiety, depression, cognitive fusion, over-controlled coping, and lack of values-based living. Caregivers also reported heightened anxiety, cognitive fusion, and over-controlled coping, although they did not endorse clinically significant depression. Patient and caregiver degree of anxiety and of overcontrolled coping were both strongly positively correlated, likely affecting how both parties manage NMOSD-related stressors, both individually and as a dyad. Patients reported more anxiety, depression, psychological inflexibility, and lack of values-based living, compared with caregivers. Patient and caregiver narrative themes included mistrust of medical professionals, lack of support immediately following diagnosis, changes in relationships, deviation from values-based living, internalization of feelings, and avoidant coping strategies to manage the psychological burden of NMOSD. A novel mental health intervention targeting the specific psychological burden of life with NMOSD is proposed.