Background Pimobendan is frequently used off‐label for treatments of cats with congestive heart failure (CHF). Concern exists regarding the safety of pimobendan in cats with outflow tract obstruction (OTO). Objectives In cats treated with pimobendan, incidence of adverse effects will not differ between cats with OTO vs cats with nonobstructive cardiomyopathy. Animals Two‐hundred sixty cats with CHF (57 with OTO, 203 with nonobstructive disease). Methods Retrospective medical record review. Groups were compared using 2‐sample t‐tests, Wilcoxon rank‐sum tests, and Fisher exact tests. Results Compared to cats with nonobstructive cardiomyopathy, cats with OTO were younger (8.9 [interquartile range (IQR) 6.6] vs 10.8 [6.3] years, P = .0036), more likely to have a heart murmur (51/57 [90%] vs 76/203 [37.8%] cats, P