A 91-year-old man was treated for upper urinary carcinoma in situ via intravesical bacillus Calmette Guérin (BCG) therapy using a double-J catheter. After the fourth infusion, he experienced fever of >38°C, multiple arthralgia, and back pain. One week after cessation of intravesical BCG immunotherapy and initiation of antibiotic treatment, he continued to complain of symptoms. Reiter's syndrome was diagnosed, and subsequently, an antitubercular agent, a nonsteroidal antiinflammatory drug and a corticosteroid were administered. His symptoms improved 17 days after onset. Reiter syndrome is an uncommon complication after intravesical BCG immunotherapy. Nevertheless, side effects may be severe and must be closely monitored.