Preterm ovarian hyperstimulation syndrome (POHS) is an uncommon disorder characterized by prematurity, hypogastric and upper leg swelling of various intensities, high serum estradiol and gonadotropin levels, and ovarian follicular cyst/cysts. In this paper, we present the first case of POHS presenting with vaginal bleeding. A female infant was born via spontaneous vaginal delivery at 25 weeks of gestation with a birth weight of 610 g. At 36 weeks of post-conception age, she developed breast enlargement, swelling of the clitoral hood, labia major and minor, hypogastrium and upper legs. Several weeks later, vaginal bleeding started and lasted 3 days. The vaginal bleeding continued to occur at monthly intervals. The elevated levels of gonadotropins and estrogens, vulvar swelling and cysts in both ovaries confirmed the diagnosis of preterm ovarian hyperstimulation syndrome.