A 46-year-old woman presented at a local hospital with polyarthralgia and dyspnea on exertion. She was referred to our hospital on suspicion of rheumatoid arthritis with interstitial pneumonia, according to her chest X-ray. Biopsy specimens obtained by video-assisted thoracoscopic surgery (VATS) and skin biopsy showed noncaseating epithelioid cell granulomas consistent with sarcoidosis. We therefore considered that this could be a case of polyarthralgia of sarcoidosis with articular involvement. Four years later she was diagnosed with rheumatoid arthritis because of articular erosion and atlanto-axial subluxation. We reviewed the earlier biopsy specimens obtained by VATS, which showed not only granulomas, but also follicular bronchiolitis. We therefore concluded that sarcoidosis and rheumatoid arthritis had already coexisted at that time. When articular involvement and interstitial pneumonia are found in patients with sarcoidosis, we should consider the possibility of coexistence of rheumatoid arthritis.