We report a pseudoparasitosis case due to Ganoderma lucidum, (lingzhi or reishi mushroom); we believe this to be a first reported case in Thailand. A 49-year-old male patient with non-Hodgkins lymphoma presented with chronic watery diarrhea. He had a history of consumption of powdered lingzhi extract as a dietary supplement and herbal medicine. Stool examination demonstrated many spores of G. lucidum, which must be differentiated from intestinal helminth ova and coccidia. After discontinuation of mushroom spores ingestion, the diarrheal symptoms improved and fecal examination subsequently showed no Ganoderma spores. Many artifacts in the stool may be confused with parasites. Differentiation of parasites from artifacts depends on characterization of the size, shape, structure, and reactivity with common stains.