Background: With the evolution of chronic Chagas cardiomyopathy (CC) and the progression towards heart failure (HF), patients may show a decline in inspiratory muscle strength, lung function, and functional capacity. Objective: We compared respiratory function and submaximal functional capacity in patients with CC with versus without HF. Methods: This observational, cross-sectional study was carried out with CC patients divided into CCG, a group without HF (n = 28), and HFG, a group with HF (n = 27). Spirometry (percent predicted forced vital capacity (ppFVC), forced expiratory volume in one second of FVC (ppFEV₁), forced expiratory flow between 25 % and 75 % of FVC (ppFEF₂₅-₇₅ ﹪), and maximum voluntary ventilation (ppMVV)) and submaximal functional capacity (six-minute step test: 6MST) were evaluated. Mann-Whitney (comparison of pulmonary function and functional capacity between groups) and linear regression (association between the presence of HF and other variables) were performed. Results: We included 55 participants, with median age of 67 years (56.25–71.75) and 54.55 % males. Dyslipidemia was the most recurrent comorbidity (49.09 %). HFG presented lower ppFVC (P = 0.000), ppFEV₁ (P = 0.011), ppFEF₂₅-₇₅ ﹪ (P = 0.017), and ppMVV (P = 0.003) than the CCG. The ppFVC (B = -18.95; P = 0.000), ppFEV₁ (B = -16.29; P = 0.021), ppFEF₂₅-₇₅ ﹪ (B = -19.57; P = 0.014), ppMVV (B = -16.59; P = 0.003), and 6MST (B = -17.13; P = 0.034) were negatively associated with the presence of HF. Conclusion: Our data suggest that impaired lung function, compatible with a restrictive pulmonary pattern, is present among adults with CC and HF.