Objectives: The aim of this study was to evaluate the relation between pathology, operative complications, and giant ovarian tumor weighing more than 5,000 grams. Materials and Methods: The authors assessed 11 factors of 18 patients with giant ovarian tumors after surgery, including age, performance status (PS), total weight of the tumor, fluid weight of the tumor, pathology, side, preoperative serum D-dimer, rate of deep venous thrombosis (DVT), intraoperative complications, and rate of postoperative ICU management. The subjects were divided into two groups: tumor weight ≥ 10,000 grams (group ≥ 10,000 grmas) and tumor weight < 10,000 grams (group < 10,000 grams), and the same factors were compared between two groups. Results: The most frequent pathology of giant ovarian tumors weighing more than 5,000 grmas was found to be adenocarcinoma. Compared to 11 patients of group < 10,000 grmas, seven patients out of group ≥ 10,000 grmas had a significantly higher rate of intra-abdominal adhesion (85.7% vs. 9.0%, p < 0.05), blood loss weight (890 grams vs. 130 grams, p < 0.05), and rate of postoperative ICU management (85.7% vs. 18.2%, p < 0.05), respectively. Conclusions: Much attention should be paid to patients with giant ovarian tumors, and aggressive surgery is recommended due to a frequent incidence of cancer.