A 69-year-old male Caucasian presenting with dyspnea on exertion related to unilateral diaphragmatic dysfunction as caused by sarcoidosis is described. First, right diaphragmatic elevation was unexplained, while the patient presented with a restrictive pattern in lung function testing using bodyplethysmography and with reduced global and diaphragmatic respiratory muscle strength as evidenced by respiratory pressures. Subsequently, surgical diaphragm plication was performed, unfortunately, without any clinical improvement. Microscopic examination of diaphragm sections revealed a lymphocytic myositis with granulomatous pleuritis showing multiple non-caseating epithelioid granulomas. Accordingly, a lymphocytic alveolitis (26% lymphocytes) with an elevated CD4/CD8 T cell ratio of 8.0% and elevated serum parameters (neopterin and sIL-2 receptor) were established. Consequently, the diagnosis of pulmonary sarcoidosis with diaphragm involvement but without extrapulmonary involvement has been established. Therefore, sarcoidosis needs to be considered in any patient presenting with unilateral diaphragmatic dysfunction. The optimal treatment strategy, however, needs to be established in the future.