Ovarian cancer (OC) is one of the most commonly diagnosed cancers among women. Regretfully due to its a broad spectrum of clinical behavior and challenging diagnosis most cases are diagnosed at a late stage. On rare occasions, these tumors can grow to massive sizes if left untreated, worsening the prognosis of the patient. Thanks to the advancement of medicine and diagnostic techniques, these rare cases are less frequent. Timely detection and surgery could avoid all these potentially troublesome scenarios. We report the case of a 64-year-old female with a giant 13 kg high-grade papillary serous ovarian cystadenocarcinoma, the tumor grew during a four year period and was adequately treated with surgery and is under close follow up with the oncologist. To our knowledge, this is the first case of a giant ovarian cystadenocarcinoma ever reported in Ecuador.