BACKGROUND : Multiple sclerosis (MS) is a chronic disorder of the central nervous system with an unpredictable disease course. Life partners often become caregivers, which can be both rewarding and challenging, as the caregiver's physical and mental health is often negatively affected. Previous studies on caregiver strain focused on caregivers of persons with MS with relatively high disability levels, while caregiver strain may already be experienced by life partners living with mildly disabled persons with MS. OBJECTIVE : The current study examines factors associated with caregiver strain in life partners of persons with mild disability due to relapsing-remitting MS. METHODS : We included 173 persons with relapsing-remitting MS (79% female; mean age 42.8 years; 90% employed; median EDSS 2.0) and their life partners. The life partners completed questionnaires on caregiver strain and neuropsychiatric and cognitive functioning of the person with MS. The persons with MS completed questionnaires about demographics, fatigue, personality, physical, cognitive and neuropsychiatric functioning, and underwent neuropsychological and neurological examinations. A linear regression analysis was conducted to examine predictors of caregiver strain. RESULTS : 24% of the life partners experienced above average levels of caregiver strain. A multivariate linear regression analysis revealed that a higher age of the person with MS (β = 0.16, p = 0.04), more physical disability (β = 0.17 p = 0.04), more cognitive and neuropsychiatric problems of the person with MS as reported by the life partner (β = 0.33, p = 0.001) and higher severity of neuropsychiatric symptoms as reported by the life partner (β = 0.32, p = 0.001) were associated with higher caregiver strain (R2 = 0.49). CONCLUSIONS : Higher caregiver strain in life partners of persons with mild disability due to relapsing-remitting MS was primarily associated with cognitive and neuropsychiatric problems of the person with MS.