Abstract: Bladder diverticulum cancer is a malignant tumor growing in the bladder diverticulum. Its incidence rate is low, and it is common in elderly men. The main clinical symptom is painless gross hematuria. Bladder diverticulum cancer often occurs in acquired bladder diverticula and is more prone to infiltrating the surrounding area than other bladder tumors. In this article, we report a case of bladder diverticulum cancer clinically manifested as a mass in the lower left abdomen with gross hematuria. CT and MR examinations showed a mass on the left side of the pelvic cavity, locally connected to the bladder wall, and suspected to originate from the bladder. Surgery and pathology confirmed the diagnosis as bladder diverticulum cancer. Enhanced CT and MR are the recommended non-invasive imaging examinations for bladder diverticulum cancer that help clarify its location and tumor staging. CT urography has a great value in differential diagnosis. In this article, we aimed to summarize the clinical manifestations, imaging features, differential diagnosis, and treatment methods of bladder diverticulum cancer to improve our understanding of the disease and help make accurate diagnosis through imaging examination.