Objectives: Patients with hypertrophic obstructive cardiomyopathy (HOCM) and severe left ventricular hypertrophy (maximal left ventricular wall thickness ≥30 mm) are at high risk of sudden cardiac death (SCD). In this study, we aimed to determine whether HOCM patients with severe hypertrophy had a lower incidence of SCD after myectomy. Methods: HOCM patients with severe hypertrophy were consecutively enrolled from Fuwai Hospital in China between 2000 and 2013. Long-term outcomes were retrospectively compared between the 2 groups, namely the myectomy group and medical group. Results: A total of 244 patients (118 in the myectomy group and 126 in the medical group) were involved. The mean follow-up durations for the myectomy and medical groups were 5.07 ± 3.73 and 6.23 ± 4.15 years, respectively. During the follow-up period, the annual cardiovascular mortality rate was 0.84% in the myectomy group and 2.04% in the medical group (p = 0.041). The annual SCD rate was 0.33% in the myectomy group and 1.40% in the medical group (p = 0.040). Multivariate Cox regression analysis showed that myectomy was independently associated with lower rates of cardiovascular death and SCD. Conclusions: In HOCM patients with severe hypertrophy, those that underwent myectomy had a lower risk of cardiovascular death and SCD than those treated with medicines only.