The coronavirus disease (COVID-19) pandemic was associated with an intense impact on health worldwide. Among the sequelae, it became necessary to clarify respiratory impairment related to lung function and aerobic capacity, as well as the treatment of curative and preventive measures of pulmonary involvement. In this context, this study aimed to compare vital signs, the sensation of dyspnea (Borg scale), lung function, and exercise tolerance before and after the use of non-invasive mechanical ventilation (NIV) in adults of both sexes after acute infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A cross-sectional analytical clinical study was performed with the inclusion of individuals who had been diagnosed with COVID-19 at least three months before data collection. Individuals were evaluated for vital signs (heart rate and peripheral oxygen saturation), Borg scale, spirometry, and submaximal exercise protocol of two minutes of the step test before and after receiving NIV in ventilation mode by continuous positive airway pressure of 6 cm HO for 30 min. A total of 50 participants were enrolled and grouped as a mild (N = 25) or severe (N = 25) clinical phenotype during SARS-CoV-2 infection according to the criteria of the World Health Organization. In our data, the forced vital capacity ( < 0.001), the ratio between the forced expiratory volume in the first one second to the forced vital capacity and the forced vital capacity ( = 0.020), and the two-minute submaximal step exercise protocol (number of steps- = 0.001) showed a statistical improvement in the severe clinical phenotype group after NIV. In addition, forced expiratory volume in the first one second to the forced vital capacity ( = 0.032) and the two-minute submaximal step exercise protocol (number of steps- < 0.001) showed a statistical improvement in the mild clinical phenotype group after NIV. No changes were described for vital signs and the Borg scale. This study allowed us to identify that NIV is a tool that promotes better exercise capacity by increasing the number of steps achieved in both clinical phenotype groups and improving lung function observed in the spirometry markers.