We herein describe the case of a 30-year-old woman who experienced high fever during the puerperal period and was diagnosed with pheochromocytoma. Acute inflammatory syndrome, as indicated by the elevated serum levels of interleukin-6 (IL-6), and cholestatic liver dysfunction were observed. Since this condition resolved before the operation, it was probably caused by massive central necrosis within the tumor. The IL-6 production from the tumor cells was confirmed by immunohistochemistry. When a case of pheochromocytoma accompanied with acute inflammatory syndrome is encountered, the possibility that the tumor itself might produce some cytokines should be considered, even in the presence of massive necrosis within the tumor.