Median nerve injury after elbow dislocation is uncommon. The diagnosis of median nerve entrapment is often delayed. Median nerve paralysis is caused by entrapment within the elbow joint. If median nerve paralysis occurs following elbow dislocation or if it occurs following closed reduction, entrapment should be suspected. Optimal management of this problem consists of early surgical exploration and decompression. We report a case of a child who had entrapment of the median nerve in the elbow joint after closed reduction of posterior dislocation with fracture of the medial epicondyle. The diagnosis was made ten weeks after injury at surgical exploration. This case showed a characteristic radiologic sign in the anteroposterior radiograph. We released the entrapped median nerve with a successful result.