Polymyositis is a type of muscle disease called an inflammatory myopathy, it causes inflammation of muscles and related tissues. It can cause muscle weakness and pain, often on both sides of the body. We report a female patient with clinical presentation such as upper limb weakness, muscle pain and difficulty in doing daily activities. Diagnostic tests such as electromyography, MRI, muscle biopsy and CPK levels are commonly elevated in acute phase of polymyositis. Here our patient was diagnosed by EMG, NCS and elevated levels of muscle enzymes. Patient symptoms got improved after the administration of corticosteroids. There is no complete cure for polymyositis, treatment can improve muscle strength and function.