Although multiple sclerosis (MS) is the most common demyelinating disorder of the central nervous system (CNS), it lacks any definitive diagnostic test. Instead, diagnosis of MS primarily depends upon clinical criteria, supported by abnormalities characteristic of MS on para-clinical investigations including magnetic resonance imaging of the brain and spine, in the absence of an alternative explanation for underlying neurologic symptoms. While many of the potential disorders that may mimic MS in routine clinical practice are either extremely rare, or associated with specific and characteristic distinguishing diagnostic features, some inflammatory demyelinating disorders of the CNS may be particularly challenging to distinguish from MS, especially during initial presentation. In particular, acute disseminated encephalomyelitis, neuromyelitis optica, and idiopathic transverse myelitis may closely resemble MS, impeding prompt and accurate diagnosis. In this review, we describe the clinical features, diagnosis, pathology, and treatment of these other CNS demyelinating disorders. In addition, we review relevant features of other CNS inflammatory disorders that may mimic MS, including Sjögren's syndrome, systemic lupus erythematosus, Behçet's disease, and primary CNS vasculitis.