OBJECTIVE: This study investigated the impact of the severity of parental multiple sclerosis, parents’ expressed emotion and psychological well-being on offspring’s psychological difficulties. DESIGN: A longitudinal study including baseline and 6-month follow-up data collected from parents and children. SUBJECTS: Adolescents (n=75), their parents with multiple sclerosis (n=56) and the partner without multiple sclerosis (n=40). MAIN MEASURES: Parents completed the Hospital Anxiety and Depression Scale and the Five Minutes Speech Sample, a standardised interview of expressed emotion towards their child. Parents with multiple sclerosis also completed the Expanded Disability Status Scale, a measure of illness severity. Adolescents completed the Strength and Difficulties Questionnaire, a self-report measure of psychological difficulties. RESULTS: Higher depression scores of the parents with multiple sclerosis at baseline correlated with increased adolescents’ internalising symptoms at 6-month follow-up (gammadep=0.31, P=.004). Higher expressed emotion scores of parents with multiple sclerosis at baseline were associated with increased adolescent externalising symptoms at 6-month follow-up (gammaEE=4.35, P=.052). There was no direct effect of severity, duration or type of multiple sclerosis on adolescents’ adjustment at baseline or follow-up. CONCLUSIONS: Emotional distress and expressed emotion in parents with multiple sclerosis, rather than the severity and type of multiple sclerosis had an impact on adolescents’ psychological difficulties.