Abstract： Objective:To investigate the clinical characteristics and outcomes of acute respiratory distress syndrome (ARDS) caused by Chlamydia psittaci pneumonia. Methods:From June 2016 to January 2021, 10 cases were diagnosed as severe Chlamydia psittaci pneumonia induced ARDS in Intensive Care Unit of Respiratory and Critical Care Medicine Department (RICU) of Beijing Chao-Yang Hospital Affiliated to Capital Medical University. We collected the clinical data including clinical features, laboratory tests, imaging and outcomes of the patients. Results:The pathogenic diagnosis was confirmed by metagenomic Next-generation Sequencing (mNGS) in these 10 patients, with a median age of 59 (46, 67) years. In addition to high fever, cough and dyspnea, the patients also had multiple organ involvement. Six patients had elevated peripheral leukocyte count, 10 cases had increased type B natriuretic peptide, 7 cases had increased aspartate aminotransferase/alanine aminotransferase, 9 cases had hyponatremia and 3 cases had elevated creatinine. The imaging findings were bilateral consolidation with air bronchogram and infiltrates, and pleural effusion were found in 5 cases. All cases were combined with respiratory failure. Six patients received invasive mechanical ventilation. Nine patients received moxifloxacin and one patient was administrated with Azithromycin. All the patients were improved and discharged after the treatment, and the mean duration of RICU stay was 13.5 (11, 16.7) days. One month follow-up of nine patients showed significant improvement in lung lesions.Conclusions:Severe Chlamydia psittiaci pneumonia may be complicated with respiratory failure and/or multiple organ involvement. For severe pneumonia with an exposure history of sick birds, the possibility of Chlamydia psittaci infection should be considered. mNGS may help etiological diagnosis. All patients in this study had a good prognosis after targeted treatment.