A follow-up study was designed to assess correlations among physical signs, quality of sleep, common mental symptoms, and health-related quality of life after moderate to severe COVID-19 pneumonia. Daily changes in dyspnoea and pulse oximetry were recorded (200 days), and four evaluations (in >2 years) were performed on quality of sleep, mental symptoms, cognitive performance, and health-related quality of life. In a single center, 72 adults participated in the study (52.5 ± 13.7 years old), with no psychiatry/neurology/chronic lung/infectious diseases, chronic use of corticosteroids/immunosuppressive therapy, or pregnancy. Daily agendas showed delayed decreases in dyspnoea scores compared to pulse oximetry and heart rate recordings; however, changes in pulse oximetry were minimal. Slight changes in cognitive performance were related to the general characteristics of the participants (obesity and tobacco use) and with the severity of acute disease (MANCOVA, p < 0.001). Health-related quality of life gradually improved (MANCOVA, p < 0.004). During recovery, bad quality of sleep and mental symptoms (mainly attention/concentration) contributed to the subscores on health perception and vitality in the health-related quality of life assessment. Early mental support services including sleep hygiene could be beneficial during rehabilitation after acute COVID-19.