Angiosarcoma of the urinary bladder is an extremely uncommon entity, with only a limited number of cases reported, making its diagnosis and management particularly challenging. This case report presents a rare occurrence of angiosarcoma within the urinary bladder and discusses its clinical presentation, radiological findings, histopathological features, and possible treatment approach for this challenging malignancy. An 84-year-old male presented at the emergency department with hematuria. Relevant history includes prostate carcinoma Gleason 7 in 2007, treated by brachytherapy. Imaging revealed bilateral hydronephrosis, urinary retention, and an irregular lesion growing through the bladder wall. Histopathology showed a highly cellular, poorly differentiated tumor composed of epithelioid cells. Immunohistochemistry was negative for epithelial, urothelial, and prostate markers. There was positivity for ERG, CD34, CD31, factor VIII, and c-myc, confirming the diagnosis of an epithelioid angiosarcoma. RNA-based sequencing did not reveal gene rearrangements. Follow-up CT showed pulmonary metastatic disease. The patient chose to undergo euthanasia six months after symptoms onset because of the decline in quality of life. We present a rare case of angiosarcoma arising in the urinary bladder, emphasizing the importance of considering this malignant vascular tumor in the differential diagnosis of bladder masses. Accurate diagnosis through histopathological evaluation and immunohistochemical staining is crucial for appropriate management. Characteristic features include its infiltrative vascular phenotype with marked atypia and positive staining for endothelial markers. Further studies are warranted to enhance our understanding of this rare entity and establish optimal treatment strategies.