The sequelae of post-coronavirus disease 2019 (COVID-19) pneumonia on lung function, exercise capacity, and quality of life were observed in both short-term and long-term. However, the study about the respiratory and locomotor muscle strength in severe and critically ill COVID-19 survivors are still limited. Therefore, we aimed to examine long-term pulmonary function, functional capacities, and respiratory and locomotor body muscle strength in severe to critically ill post-COVID-19 survivors. A prospective observational study was conducted in twenty-two post-COVID-19 pneumonia and healthy adults. Clinical characteristics during admission, pulmonary function, functional capacity, respiratory muscles, and locomotor muscles strength were examined at 1, 3, and 6 months after discharge from the hospital. The generalized linear mixed model showed that percent predicted of forced expiratory volume in the first second (%FEV1), percent predicted of forced vital capacity (%FVC), maximum inspiratory pressure (MIP), handgrip strength, six-minute walk distance (6-MWD), and 5-times sit to stand (5TSTS) were significantly lower in post-COVID-19 pneumonia patients than in healthy subjects during the follow-up period. The percent predicted of maximal voluntary ventilation (%MVV), and locomotor muscle strength were not different between the two groups throughout the follow-up period. Among post-COVID-19 pneumonia patients, %FEV1, %FVC, %MVV, 5TSTS, locomotor muscle strength significantly improved at three months compared to baseline at one month. Pulmonary function, functional capacity, respiratory, and locomotor muscle strength of survivors from COVID-19 were impaired and recovery was observed after three to six months. These emphasized the need to evaluate the long-term consequences of COVID-19.