Carnitine palmityl-transferase (CPT) II deficiency is a rare disorder of the fatty acid beta-oxidation cycle. CPT II deficiency can be associated with rhabdomyolysis in particular conditions that increase the requirement for fatty acid oxidation, such as low-carbohydrate and high-fat diet, fasting, exposure to excessive cold, lack of sleep and prolonged exercise. The best known CPT II deficiency is the muscular form with episodic muscle necrosis and paroxysmal myoglobinuria after prolonged exercise. We report a case of a four-year-old male child, who, after one day of hyperthermia and fasting, developed a massive rhabdomyolysis beginning with acute respiratory failure and later complicated by acute renal failure. Appropriate management in Pediatric Intensive Care Unit (PICU) (mechanical ventilatory support, fluid supply combined with mannitol and bicarbonate infusions, administration of acetaminophen and antibiotics, and continuous venovenous haemofiltration) brought about complete resolution with an excellent outcome. Biochemical investigation of muscle biopsy and genetic analysis showed a deficiency of CPT II. The onset of CPT II deficiency with respiratory failure is extremely rare, but a correct and early diagnosis of rhabdomyolysis is the key to successful treatment. A metabolic myopathy such as CPT II deficiency should be suspected in children affected by rhabdomyolysis if trauma, crash, infections, drugs or extreme exertion can be excluded.