Articular cartilage flap tear of patella is a rare injury that occurs in children. Diagnosis is difficult both clinically and radiologically. Apart from knee swelling and retro-patellar tenderness, there is no other clinical finding. We report a case of 16 year old boy who suffered from patella cartilage flap tear without visible bony fragments. Mini-open reduction, microdrilling, sealing of margins with fibrin glue and double breasting of medial patellar retinaculum was performed. Early weight bearing was achieved together with a satisfactory range of knee motion. An awareness of cartilage flap tear, together with its characteristic clinical and radiological features and proper treatment is necessary to avoid misdiagnosis and treatment delay.