Objective Carbonic anhydrase (CA) II deficiency is a rare autosomal recessive disorder caused by mutation in the CA II gene that leads to osteopetrosis, renal tubular acidosis (RTA), and cerebral calcification. Our aim is to present a patient with the classic triad of CA II deficiency syndrome to enhance the awareness about this rare syndrome. Methods We describe the clinical and radiological findings of a Saudi woman patient with CA II deficiency syndrome. Results A Saudi woman in her 20s presented to our hospital for evaluation of increased bone density. She was known to have delayed developmental milestone with growth retardation and poor scholastic performance. She had multiple fragile fractures started at the age of 15 involving the lower extremities. A physical examination revealed dysmorphic features and intellectual disability with intelligence quotient (IQ) of 36. The initial blood workup showed a picture of distal RTA with hypokalemia, and the radiological imaging confirmed the presence of osteopetrosis and multiple kidney stones. The combination of osteopetrosis with RTA raised the possibility of CA II deficiency. Therefore, computed tomography (CT) of the brain was done and showed intracranial calcification involving the basal ganglia. She was started on potassium chloride and sodium bicarbonate. In addition, she underwent right-sided percutaneous nephrolithotripsy. Her DNA analysis came to show a sequence variant c.232+1G>A, which was detected in both of the CA II genes (homozygous). Conclusion Early recognition of the disease is a key, as an early appropriate treatment institution is essential in order to prevent further complications.