Sleep disorders in multiple sclerosis (MS) are more common than in general population and are considered to be one of the important etiological factors in development of fatigue, most common and debilitating symptom of MS. Although almost all of the major subgroups of sleep disorders such as insomnia, sleep disordered breathing, REM sleep behavior disorder, narcolepsy and restless legs syndrome have been described in the MS patients their higher prevalence in MS population than in healthy controls in some of the sleep disorders is not fully elucidated. Immunological background in disease development in both multiple sclerosis and sleep disorders have been proposed as possible common pathophysiological mechanism and recent findings of disrupted melatonin pathways in MS patients suggest multi-level causative mechanism of the development of sleep disorders in MS.