OBJECTIVES - To assess the association between impaired chronotropic response (CR) and adverse events among patients with diabetes referred for exercise treadmill testing (ETT). RESEARCH DESIGN AND METHODS - Impaired CR was defined as achievement of <80% of a patient's heart rate reserve. We used multivariable Cox proportional hazards regression to assess the independent association between impaired CR and adverse outcomes adjusting for demographics, comorbidities, and treadmill variables including the Duke Treadmill score. RESULTS - Of 1,341 patients with diabetes, 35.7% (n = 479) demonstrated impaired CR during ETT. Patients with impaired CR were at increased risk of all-cause mortality, myocardial infarction, or coronary revascularization procedures. In multivariable analyses, impaired CR remained significantly associated with adverse outcomes (hazard ratio 1.53 [95% CI 1.102.14]). CONCLUSIONS - Among patients with diabetes,impaired CR is common during ETT and is associated with adverse outcomes. Impaired CR can be used as another noninvasive tool to risk-stratify patients with diabetes following ETT.