Neuropsychiatric symptoms are common in multiple sclerosis (MS). They include two broad categories of disturbances: abnormalities in cognition, and abnormalities of mood, affect and behaviour. The present review deals with the epidemiology, clinical features, etiology and treatment of disturbances included in the second category, i.e., major depression, fatigue and sleep disorders, bipolar disorder, euphoria, pathological laughing and crying, anxiety, psychosis and personality changes. Major depression is one of the most common neuropsychiatric disorders in MS with an approximate 50% lifetime prevalence rate. Early recognition and management of depression in MS is of major importance because it is a key predictor of morbidity, mortality, quality of life, possibly physical outcome and disease exacerbations, adherence to immunomodulatory treatments and suicide risk in MS patients, as well as of the caregiver's distress and quality of life. The etiopathogenesis of neuropsychiatric disorders in MS has been incompletely investigated. It is postulated that a complex interplay of biological, disease-related, behavioural and psychosocial factors contribute to the pathophysiology of most of them. Management of neuropsychiatric symptoms in MS is often effective, although commonly based on evidence provided by case studies and uncontrolled trials. A comprehensive biopsychosocial neuropsychiatric approach is essential for the optimal care of patients with MS.