We report the case of a patient with adenomyosis complicated by deep vein thrombosis in whom low-dose gonadotropin-releasing hormone agonist (GnRHa) therapy was useful as a uterus-conserving therapeutic option. The patient was a 34-year-old nulliparous woman who presented with edema and pain in the left lower leg. The patient had been treated with four cycles of GnRHa therapy for adenomyosis and repeatedly experienced chronic pelvic pain, dysmenorrhea and anemia due to hypermenorrhea. Leg venography confirmed deep vein thrombosis, and thrombolytic therapy was performed to eliminate symptoms. Because the patient strongly wanted to conserve the uterus, low-dose GnRHa therapy was initiated. The patient is currently taking 450 microg/day buserelin acetate nasally (regular dose: 900 microg/day), and estradiol levels have been maintained at 24-50 pg/ml. Anemia, leg numbness and chronic pelvic pain have dissipated, and the patient has not experienced estrogen deficiency symptoms for more than two years.