Ovarian fibroma rarely occurs in prepubertal girls. We report an ovarian fibroma in a 7-month-old female infant presenting as a right abdominal mass. The tumour was composed of oval-to-spindle cells forming interlacing fascicles and intermingling with collagen fibres. Immunohistochemically, the tumour cells were weakly positive for estrogen receptor and progesterone receptor but negative for inhibin. To the best of our knowledge, this is the youngest case of ovarian fibroma up-to-date in the English literature. Because Gorlin's syndrome was not present in the patient's family, other factors such as germline or somatic mutations may predispose the occurrence of this ovarian fibroma in infancy.