Poor-sleep quality in patients with COVID-19 was associated with a slow recovery from lymphopenia, an increased risk of becoming critically ill and requiring ICU care, and prolonged duration of hospital stay. It is important to adopt comprehensive treatment measures during hospitalization to improve the sleep quality of patients with mild or moderate lymphopenia in the early stage of COVID-19 infection to promote recovery of immune function and prevent the need for ICU care, thereby reducing the great risk posed by the COVID-19 crisis regarding critical care resources.