Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiac disease and is characterized by large and asymmetric septal and left ventricle hypertrophy. HCM is a cause of disability, including heart failure, atrial fibrillation, and sudden death, with an annual mortality varying from 1% to 6%. Obstructive sleep apnea (OSA) is extremely common among patients with established cardiovascular disease, including hypertension and atrial fibrillation and when present may contribute to worse cardiovascular outcome. Although patients with HCM do not necessarily have typical characteristics of patients with OSA, such as obesity and increasing age, there is recent evidence that OSA is extremely common among patients with HCM, with a prevalence ranging from 32% to 71%. The presence of OSA among patients with HCM is independently associated with worse structural and functional impairment of the heart, including atrial and aorta enlargement, worse New York Heart Association functional class, and worse quality of life. The prevalence of atria fibrillation, an independent marker of mortality among patients with HCM, is significantly higher (four times) in the presence of OSA. Therefore, the recognition of OSA is a new area of research that may impact the management of patients with HCM.