Abstract Aim The aim of this study was to estimate the effects of a pulmonary rehabilitation programme (PR) on the functional capacity and respiratory muscle strength of patients with post-COVID syndrome. Methods A cross-sectional study was conducted using hospital data on patients who participated in a pulmonary rehabilitation programme at the Clinic for Lung Diseases, University Hospital Centre Zagreb, Croatia, between January 2021 and December 2022. Data on the spirometry, respiratory muscle strength, and functional exercise capacity of patients were collected at baseline and three weeks after the start of rehabilitation. The study included 80 patients (43 females, 37 males) with a mean age of 51±10 years. Results A significant increase in respiratory muscle strength (P<0.001) was observed after pulmonary rehabilitation, with effect sizes ranging from small to large (Cohen’s d from 0.39 to 1.07), whereas the effect for PImax expressed as a percentage was large (Cohen’s d=0.99). In addition, the pulmonary rehabilitation programme significantly improved the parameters of the six-minute walk test in patients, and the parameters of lung function, FVC, FEV1, and DLCO also improved significantly after PR (P<0.05). Conclusion The results showed that the pulmonary rehabilitation programme has clinically significant effects on functional capacity and respiratory muscle strength in patients with post-COVID syndrome.