We present a case of a right renal tumor associated with increased accumulation of F-18 FDG in the peritoneum and ileocecum on PET imaging. The FDG-PET images suggested peritoneal carcinomatosis, but the histopathology of the open biopsy proved tuberculous peritonitis. Tuberculous peritonitis should be considered as a potential interpretive pitfall in mimicking peritoneal carcinomatosis.