<h3>Purpose</h3> Patients with hypertrophic obstructive cardiomyopathy (HOCM) often have concomitant pulmonary hypertension (PH). We hypothesize that concomitant PH is associated with increased risk for short-term adverse outcomes after septal myectomy. <h3>Methods</h3> We retrospectively evaluated 758 patients who underwent septal myectomy for treatment of HOCM between 2010 and 2020 at our institution. There were 396 total patients who had pre-op right heart catheterization (RHC). After exclusion of patients without complete RHC data, there were 281 patients included in the final analysis. Adverse events (AE) were defined by a composite endpoint which included post-operative stroke, TIA, MI, cardiac arrest, prolonged ventilation, reintubation, pneumonia, multi-organ failure, and mortality. Comparison was made between patients with and without AE. Categorical variables were compared with chi-square or Fisher's exact test where appropriate. Continuous variables were compared with one-way ANOVA. Significance was defined as p<0.05. <h3>Results</h3> The overall incidence of AE in the study population was low (n=17, 6%). Prolonged ventilation was the most common AE (n=9, 3.2%). Patients with AE were older in age (64 vs 57, p=.015) and were more likely to have chronic lung disease (OR 4.42, 95% CI 1.5-12.8; p=.003). On pre-op RHC, patients with AE had significantly greater pulmonary artery (PA) systolic pressure (47 vs 38, p=.010), mean PA pressure (32 vs 26, p=.017), PA pulsatility index (5.9 vs 3.8, p=.004), PA pulse pressure (28 vs 22, p=.009), transpulmonary gradient (13 vs 10, p=.02), and pulmonary vascular resistance (3.4 vs 2.0, p <.001). <h3>Conclusion</h3> Increased severity of concomitant PH in patients with HOCM undergoing septal myectomy surgery is associated with increased risk for short-term adverse outcomes. Preoperative pulmonary artery pressure is of prognostic predictive value. Screening for and treating PH before septal myectomy may reduce the risk of complications.