This report presents the case of a rare and aggressive cancer originating from the urachus in a 73-year-old female. After 12 years of observation due to a cystic lesion in the bladder dome, the patient rapidly developed haematuria and mucinuria. The use of multiple diagnostic measures suggested urachal malignancy. Partial cystectomy and urachal excision along with pelvic lymphadenectomy were performed. Urachal adenocarcinoma with negative surgical margins and lymph nodes was reported in pathology. Follow-up after 12 months did not reveal any cancer relapse. Epidemiological, clinical and therapeutic features of this disease are also discussed.