Exertional dyspnea is a common complaint of patients with heart failure with preserved ejection fraction (HFpEF) and chronic obstructive pulmonary disease (COPD). HFpEF is common in COPD and is an independent risk factor for disease progression and exacerbation. Early detection, therefore, has great clinical relevance.The aim of the study is to detect the frequency of masked HFpEF in non-severe COPD patients with exertional dyspnea, free of overt cardiovascular disease, and to analyze the correlation between masked HFpEF and the cardiopulmonary exercise testing (CPET) parameters.We applied the CPET in 104 non-severe COPD patients with exertional dyspnea, free of overt cardiovascular disease. Echocardiography was performed before and at peak CPET. Cut-off values for stress-induced left and right ventricular diastolic dysfunction (LVDD/ RVDD) were E/e'>15; E/e'>6, respectively. Correlation analysis was done between CPET parameters and stress E/e'. A p-value <0.05 was considered significant.64% of the patients had stress-induced LVDD; 78% had stress-induced RVDD. Both groups with stress LVDD and RVDD achieved lower load, lower V'O2 and O2-pulse, besides showing reduced ventilatory efficiency (higher VE/VCO2 slopes). None of the CPET parameters were correlated to stress-induced left or right E/e'.There is a high prevalence of stress-induced diastolic dysfunction in non-severe COPD patients with exertional dyspnea, free of overt cardiovascular disease. None of the CPET parameters correlates to stress-induced E/e'. This demands the performance of Exercise stress echocardiography (ESE) and CPET for the early detection and proper management of masked HFpEF in this population. (Arq Bras Cardiol. 2021; 116(2):259-265).