BACKGROUND: The modified Morrow surgery is the gold standard surgical treatment for hypertrophic obstructive cardiomyopathy (HOCM). While effective, it carries a risk of postoperative severe multi-organ dysfunction and its impact on long-term cardiovascular outcomes remains poorly understood and controversial. METHODS: This observational cohort study included 380 HOCM patients undergoing the modified Morrow surgery between July 2015 and March 2025. Severe multi-organ dysfunction was defined as a maximum Sequential Organ Failure Assessment (SOFA) score ≥ 11. The primary endpoint was the long-term incidence of major adverse cardiac and cerebrovascular events (MACCEs). Secondary endpoints included heart failure hospitalization (HFH), postoperative atrial fibrillation (AF) ablation, and cardiovascular mortality. RESULTS: Compared to patients without severe multi-organ dysfunction (SOFA Maximum < 11, n = 234), those with SOFA Maximum ≥ 11 (n = 146) had significantly higher rates of MACCEs (53.4% vs. 17.5%, p < 0.001), cardiovascular mortality (11.6% vs. 0.9%, p < 0.001), HFH (21.9% vs. 8.5%, p < 0.001), and postoperative AF ablation (17.8% vs. 3.8%, p < 0.001). Multivariable Cox proportional hazards regression demonstrated that severe multi-organ dysfunction was independently associated with cardiovascular mortality (HR = 4.157, p = 0.047), MACCEs (HR = 2.296, p < 0.001), HFH (HR = 1.834, p = 0.042), and postoperative AF ablation (HR = 3.987, p < 0.001). Other independent predictors included family history of hypertrophic cardiomyopathy, left ventricular end-systolic dimension, postoperative left ventricular outflow tract velocity, and postoperative surgical intensive care unit ventilation time. CONCLUSIONS: Postoperative severe multi-organ dysfunction is independently associated with an increased risk of adverse long-term outcomes after modified Morrow surgery. Incorporating the SOFA score into postoperative risk stratification may help identify high-risk patients warranting intensified long-term management.