Perineal leiomyoma are rare mesenchymal tumours classified as somatic or retroperitoneal. The retroperitoneal variety are mainly related to women during the peri-menopausal phase. Diagnosis is directed at differentiating them from leiomyosarcomas and gastrointestinal stromal tumours. We report on a case of a 30-year-old and 9-week pregnant woman. She consulted due to a progressive growing mass in the right ischiorrectal fossa coinciding with pregnancy, but with sparse symptoms. Surgery was performed through a perineal access with a complete resection of a 9 cm tumour.