A 32-year-old man was incidentally found to have abnormal shadows on a chest X-ray film and was admitted on May 2004. His chest images showed mediastinal and bilateral hilar lymphadenopathy. The serum level of angiotensin-converting enzyme was elevated. We also found non-caseating epithelioid cell granulomas in transbronchial lung biopsy specimens, and confirmed the diagnosis of sarcoidosis. We carried out bronchoalveolar lavage (BAL) for evaluation of disease activity of sarcoidosis. After BAL, he suffered high fever and polyarthralgia. Both ankles were extremely inflamed. We suspected infectious arthropathy caused by atypical pathogens and thus administered antibiotics, but they had no effect at all. Also, no findings suggesting collagen-vascular disorders, including rheumatoid arthritis, were detected. His symptoms improved after three-weeks of treatment with non-steroidal anti-inflammatory drugs. Thus, this case was diagnosed as having acute sarcoid polyarthritis. BAL may have influenced the onset of febrile arthritis in this patient This case indicates that sarcoidosis should be considered as a possible cause of acute febrile polyarthritis.