A case of giant cell fibroma of the oral mucosa found in a 3-year-old female is reported. The lesion was characterized histologically by the presence of numerous large stellate cells and multinucleated giant cells scattered in a loosely arranged collagen-background. The large stellate cells had a large hyperchromatic nucleus, while the cytoplasm was well demarcated and frequently the cells had dendritic-like processes. The multinucleated giant cells had similar morphology and occasionally resembled Langhans' giant cells. Ultrastructural examination suggested that the multinucleated giant cells in the lesion were unusual fibroblasts. This is the first reported case of oral giant cell fibroma in a Japanese patient.