Reactive arthritis, formerly called Reiter's syndrome, is one of the rare complications following intravesical instillation of Bacillus Calmette Guerin (BCG). A 58-year-old man was admitted to our hospital because of fever, hyperemia of conjunctiva, and arthralgia following the second course of intravesical instillation of BCG in the treatment of pT1 and pTis bladder cancer. We diagnosed him with reactive arthritis due to the clinical course. Reactive arthritis is usually well controlled with the discontinuation of instillation and administration of nonsteroidal anti-inflammatory drugs (NSAIDs). However, his symptoms were not improved after administration of NSAIDs, prednisolone, and isoniazid. Following initiation of methotrexate, however, there was remission. He has been free from recurrence of bladder cancer for 20 months.