The childhood obesity epidemic involves unusual and underrecognized complications associated with this clinical and public health problem. Obesity hypoventilation syndrome (OHS) is defined as the triad of obesity, daytime hypoventilation, and sleep-disordered breathing in the absence of an alternative neuromuscular, mechanical or metabolic explanation for hypoventilation. We herewith report a 12-year-old boy who was diagnosed with OHS. The patient improved with phlebotomy and bi-level positive airway pressure. To the best of our knowledge, this is the first reported case of secondary polycythemia due to OHS requiring therapeutic phlebotomy.