Low-grade endometrial stromal sarcoma (ESS) is a rare neoplasm and is generally an indolent tumor with estrogen and progesterone receptors. Objective responses by hormonal treatment with progestin or aromatase inhibitor have been reported, however, long-term management of this disease could be difficult if it becomes refractory to one of these hormonal therapies. A 34-year-old woman was diagnosed with stage I low-grade ESS at the time of hysterectomy for presumed uterine fibroma. Five years later, she recurred with multiple tumors in the lower abdomen. After an optimal surgery, she was free from progression for 6 years with progestin treatment (medroxyprogesterone acetate: MPA, 200-600 mg daily). Thereafter, she recurred twice during the MPA treatment and received debulking surgery each time. MPA was discontinued at age of 53, because another recurrent tumor grew up to 13 cm in diameter. Aromatase inhibitor anastrozole was then given at a daily dose of 1 mg with partial response (the tumor size decreased to 7 cm in diameter) for a duration of 9 months. After complete resection of the recurrent tumor, she remains progression-free for 16 months. Anastrozole was effective to recurrent low-grade ESS even after being refractory to progestin therapy. Aromatase inhibitor treatment may be a useful option as a second-line hormonal treatment to low-grade ESS.