Introduction: Adult polycystic kidney disease is characterized by bilateral multiple renal cysts which is often accompanied by cyst formation in liver and pancreas. Although the disease is bilateral, renal involvement may be asynchronous and asymmetrical. There are some reports on unilateral ADPKD in literature. Risk of renal cell carcinoma in patients with ADPKD is controversial and reportedly <1%. We are reporting a case of unilateral ADPKD with focus of RCC presenting as a huge mass. Case presentation: Seventy years old male patient from South India was admitted with the history of abdominal distension, dyspnoea, cough with expectoration, fever and weight loss with a positive family history of ADPKD. On examination, a 30 × 25 cms mass was palpable in right hypochondriac, right lumber, right iliac, umbilical, left iliac and hypogastric areas. The mass was crossing the midline. Computerized tomography scan of abdomen showed a huge, predominately cystic, well defined mass occupying right hypochondriac, renal, iliac and umbilical regions. Computerized tomography guided Fine needle aspiration cytology showed moderately differentiated renal cell carcinoma. Intravenous pylography showed a grossly enlarged right polycystic kidney with multiple calculi (an incidental finding). Right radical nephrectomy was done, and about a 5 kg, hugely enlarged polycystic right kidney mass was removed. Patient recovered well postoperatively. Conclusion: Bilateral ADPKD is common finding, but there are only a few reports on unilateral ADPKD; still rare is development of RCC in ADPKD. Our case adds to our knowledge; of unilateral presentation of ADPKD with the focus of RCC; which presented as a huge mass which was crossing the midline.