Background: Given that total laparoscopic hysterectomy (TLH) is less invasive than open surgery, its popularity has increased in Japan. The aim of the present study was to determine the most appropriate uterine size for the safe completion of TLH for the treatment of uterine leiomyomas. Methods: This retrospective study included 505 patients who underwent TLH for uterine leiomyomas. Patients were divided into three groups according to the weight of the excised uterus (500 g, n = 347; 500–1000 g, n = 125; >1000 g, n = 33). TLH procedures were performed by a resident physician under the supervision of an attending physician. Clinical outcomes including blood loss and duration of surgery were collected from patients’ electronic medical records and compared according to uterine size. Magnetic resonance imaging (MRI) was performed prior to TLH for detection, localization, and measurement of the myoma. Results: Mean operation times were shortest (500 g: 163 min; 500–1000 g: 190 min; >1000 g: 209 min) and the mean volume of blood lost was lowest (500 g: 116 mL; 500–1000 g: 208 mL; >1000 g: 402 mL) in patients with a uterus weighing less than 500 g. There were no significant differences in operation time or bleeding between those with a uterine weight of 500–1000 g or >1000 g. MRI revealed that myomas tended to be restricted within the sacral promontory in patients with uterine weights 500 g, whereas those in the other two groups tended to extend beyond this region. Conclusions: TLH outcomes are best when the uterine weight is 500 g. The use of MRI prior to TLH may provide insights into uterine size and/or mass and thus allow for improved surgical planning.