Splenic cysts are highly infrequent, about 0.07 percent. A post-traumatic splenic cyst is a rare complication that should be noticed if a lump in the left upper abdomen swells after abdominal trauma. This publication reported a case of a 23-year-old male student with a lump in the upper left abdomen. This study aims to describe the patient’s disease with the background of the case above. The author, in this case, uses the case report research method. Case reports are detailed descriptions of rare diseases, recent occurrences, unusual indications or symptoms of disease, unreported studies, or unexpected events observed in a patient during treatment. As a result of the abdominal examination, a smooth mass was palpable on the abdomen, located in the left hypochondrium and epigastric region. This mass is stable, with a diameter of 25 cm. Computed tomography (CT) of the abdomen found hypodense lesions, round, firm, and regular in the spleen, with intralesional pneumatization and air-fluid. A median laparotomy found a giant splenic cyst. A total splenectomy was performed. Found splenic hemorrhagic cysts without signs of malignancy. An unusual occurrence of a post-traumatic giant splenic cyst. A post-traumatic splenic cyst should be considered if one has a mass in the left upper abdomen after experiencing abdominal trauma. Total splenectomy, either open or laparoscopic, is the preferred treatment, especially if the cyst is large. This study is an original study by the author and is data taken directly from patients.International Journal of Human and Health Sciences Vol. 08 No. 01 Jan’24 Page: 103-107