Context: We reviewed what has been studied and published during the last 3 years about the consequences, mainly respiratory, cardiac, digestive, and neurological/psychiatric (organic and functional), in patients with COVID-19 of prolonged course. Objective: To conduct a narrative review synthesizing current clinical evidence of abnormalities of signs, symptoms, and complementary studies in COVID-19 patients who presented a prolonged and complicated course. Methods: A review of the literature focused on the involvement of the main organic functions mentioned, based almost exclusively on the systematic search of publications written in English available on PubMed/MEDLINE. Results: Long-term respiratory, cardiac, digestive, and neurological/psychiatric dysfunction are present in a significant number of patients. Lung involvement is the most common; cardiovascular involvement may happen with or without symptoms or clinical abnormalities; gastrointestinal compromise includes the loss of appetite, nausea, gastroesophageal reflux, diarrhea, etc.; and neurological/psychiatric compromise can produce a wide variety of signs and symptoms, either organic or functional. Vaccination is not associated with the emergence of long-COVID, but it may happen in vaccinated people. Conclusions: The severity of illness increases the risk of long-COVID. Pulmonary sequelae, cardiomyopathy, the detection of ribonucleic acid in the gastrointestinal tract, and headaches and cognitive impairment may become refractory in severely ill COVID-19 patients.