Pseudo-Meigs syndrome is a rare syndrome characterized by hydrothorax and ascites associated with pelvic masses, and patients occasionally present with elevated serum cancer antigen-125 (CA125) levels. Hydropic leiomyoma (HLM) is an uncommon subtype of uterine leiomyoma characterized by hydropic degeneration and secondary cystic changes. Rapidly enlarging HLMs accompanied by hydrothorax, ascites, and elevated CA125 levels may be misdiagnosed as malignant tumors. Here, we report a case of HLM in a 45-year-old Chinese woman who presented with ascites and hydrothorax. Preoperative abdominopelvic CT revealed a giant solid mass in the fundus uteri measuring 20 × 15 × 12 cm. Her serum CA125 level was elevated to 247.7 U/ml, while her hydrothorax CA125 level was 304.60 U/ml. The patient was initially diagnosed with uterine malignancy and underwent total abdominal hysterectomy and adhesiolysis. Pathological examination confirmed the presence of a uterine hydropic leiomyoma with cystic changes. After tumor removal, the ascites and hydrothorax subsided quickly, with no evidence of recurrence. The patient's serum CA125 level decreased to 116.90 U/mL on Day 7 and 5.6 U/mL on Day 40 postsurgery. Follow-up data were obtained at 6 months, 1 year, and 2 years after surgery, and no recurrence of ascites or hydrothorax was observed. This case highlights the importance of accurate diagnosis and appropriate management of HLM to achieve successful outcomes.© 2024. The Author(s).