A patient with a known history of hypothyroidism due to Hashimoto's thyroiditis presented with a subacute, progressive sensorimotor deficit that affected the upper limbs predominantly. The electrophysiological findings progressively evolved from multifocal motor conduction block to multifocal demyelinating sensory and motor nerve involvement with conduction block, and finally to findings fulfilling the diagnostic criteria of chronic inflammatory demyelinating polyneuropathy (CIDP). The patient did not respond adequately to intravenous immunoglobulin, whereas oral prednisone led to fast and complete recovery. This report discusses the evolution of early findings of CIDP, as well as its coexistence with Hashimoto's thyroiditis.