The clinical relevance of Krebs von den Lungen-6 (KL-6) levels in patients with coronavirus disease 2019 (COVID-19) is unclear . This study aimed to evaluate the correlation between KL-6 levels, laboratory parameters, and clinical outcomes . We enrolled 364 patients with confirmed COVID-19 who were hospitalized within 1 week of symptom onset . Their serum KL-6 level was measured on admission . Demographic data, symptoms, comorbidities, and laboratory parameters were recorded at the time of admission . Days to nucleic acid conversion and days of hospitalization were defined as clinical outcomes for evaluating the clinical relevance of serum KL-6 levels in COVID-19 . Patients with elevated KL-6 levels were significantly older; had more reported instances of fever, cough, fatigue, and wheezing; and a longer hospital stays than those with normal KL-6 levels; the difference was statistically significant (p <0.001). Furthermore, KL-6 levels was associated with the days of hospitalization and various laboratory parameters that influence the severity and prognosis of COVID-19 . Elevated KL-6 levels have also been shown to be an independent risk factor for prolonged hospitalization . Our data suggest that serum KL-6 levels on admission can serve as an indicator for assessing the clinical outcomes of COVID-19.