RATIONALE: Bladder fungal ball formation is a rare type of fungal infection, most commonly occurring in patients with diabetes or immunodeficiency. Only a few reports have described bladder fungal balls detected on computed tomography (CT). This case presentation highlights the characteristic CT findings of bladder fungal balls and discusses the diagnostic challenges. PATIENT CONCERNS: A 66-year-old male was admitted with complains of passing particulate matter in urine, urinary frequency, urgency, and hematuria. He had a long-standing history of diabetes and hypertension. DIAGNOSES: Nonenhanced abdominal CT revealed multiple bladder nodules with mixed density, the largest measuring approximately 2.5 cm in diameter, accompanied by signs of emphysematous cystitis. The nodules exhibited a peculiar appearance. Pathological examination of expelled material and urine culture confirmed Candida species infection. INTERVENTIONS: The patient received intravenous fluconazole for fungal urinary tract infection (400 mg daily) and intensive insulin therapy for critically high fasting blood glucose (23.31 mmol/L). OUTCOMES: After 10 days of treatment, follow-up CT showed a reduction of bladder gas shadows but enlargement of the nodules, filling the entire bladder lumen. Despite improved glycemic control, the patient refused further intervention (e.g., cystoscopic evacuation) and was lost to follow-up. LESSONS: In high-risk patients (e.g., diabetes), the CT finding of multiple irregular bladder nodules with associated emphysematous cystitis should raise strong suspicion for bladder fungal balls, prompting timely urine culture and appropriate antifungal therapy.