BACKGROUND: Mullerian adenosarcoma of the cervix is a rare biphasic tumor composed of a benign epithelial component and a malignant stromal component. Here, we report a rare case of Mullerian adenosarcoma of the cervix in an adolescent girl treated with hysteroscopic resection. CASE PRESENTATION: A 16-year-old girl presented to the Affiliated Hospital of North Sichuan Medical College in April 2017 with a 1-year history of a painless vaginal mass. Ten hours before presentation, she had experienced rapid enlargement of the vaginal mass and mild vaginal bleeding. Sixteen hours after hospitalization, a mass measuring 14 × 10 × 4 cm was spontaneously expelled from the vagina. Histopathological examination of the mass confirmed a diagnosis of Mullerian adenosarcoma. On May 10, 2017, the patient underwent hysteroscopic resection of a cervical lesion and partial cervical resection. After nearly 7 years of follow-up, the tumor has not recurred. CONCLUSION: Mullerian adenosarcoma of the cervix is difficult to diagnose in adolescents. For young women affected by low-risk early-stage Mullerian adenosarcoma of the cervix, fertility-preserving treatment using hysteroscopic resection with robust follow-up is a reasonable management option.