The natural history of the disease, and the treatment of post-COVID-19 patients, are still being built. Symptoms are persistent, even in mild cases, and the infection consequences include fatigue, dyspnea, tachycardia, muscle loss, and reduced functional capacity. Regarding cardiopulmonary rehabilitation, there seems to be an improvement in functional capacity, quality of life, and prognosis with the 6-Minute Walk Test used as a prognostic and therapeutic evaluator. Therefore, this case series report aims to present our experience with four cases of different severity levels, involved in a post-COVID-19 cardiopulmonary rehabilitation program. These patients were assessed with the 6-Minute Walk Test, peripheral muscle strength, and double product at rest, to assess the results after a three-month rehabilitation protocol of at least 300 minutes per week. The four patients had their distance covered during the walk test increased between 16% and 94%. Peripheral muscle strength was improved by 20% to six times the baseline values, and double product at rest was reduced by 8% to 42%. The cardiopulmonary rehabilitation program had a positive impact on these cases, improving functional capacity despite the different severity levels in these post-COVID-19 cases.