Abstract Introduction: Upper abdominal metastases of bladder cancer are very rare. This case report describes the first ever patient with bladder cancer progression initially presenting with gastric outlet obstruction due to peritoneal carcinomatosis of upper gastrointestinal system. Case report: We present the case of a 78-years-old male patient with diagnosed high risk NMIBC (high grade pT1 + CIS) who was admitted to hospital with vomiting. At the time, patient was between 2. and 3. BCG instillation cycle, following two transurethral resections. Routine urological follow-up one month before admission showed no signs of tumour. Gastroscopy revealed duodenal stenosis without intraluminal lesions. First CT- scans showed inflammation of the fat tissue surrounding duodenum without clear signs of metastases. Laparoscopic exploration described lesions typical for peritoneal carcinomatosis. Pathohistological analysis of taken samples proved urothelial cancer cells, confirming the diagnosis of metastatic bladder cancer. Conclusion: This case report presented an unusual presentation of bladder cancer that could help clinicians in everyday practice, as it might bring focus to a progression potential of the bladder cancer, eventually encouraging improvement in diagnostics and therapy. Keywords: non-muscle invasive bladder cancer, NMIBC, metastatic bladder cancer, peritoneal carcinomatosis, gastric outlet obstruction