Objective:To analyze the clinical characteristics of pneumonia caused by Chlamydia psittaci (C. psitttaci). Methods:A retrospective analysis was performed on the clinical data of 13 consecutive patients with C. psitttaci pneumonia admitted to the First Affiliated Hospital of Xiamen University from November 2018 to February 2021. Results:All 13 cases had symptoms of fatigue and 6 cases had headache. At consultation, the ΔSequential Organ Failure Assessment (SOFA) scores of all patients were ≥2 points. According to the Pneumonia Severity Index (PSI) score, 2 patients were grade Ⅱ and the other 11 patients were grade Ⅳ or Ⅴ. Laboratory tests showed that C-reactive protein (CRP) and procalcitonin (PCT) levels were elevated in all patients; CRP≥100 mg/L was found in 11 cases and PCT≥0.5 ng/ml was found in 9 cases.There were 12 cases with respiratory failure and 12 cases with elevated transaminase. Chest CT scans showed multiple patchy exudative shadow, focal consolidation and air bronchial sign; and the lesions were mainly in the lower lungs (8 cases). C. psitttaci infections were confirmed by metagenomics next-generation sequencing (mNGS) and the patients′ conditions improved rapidly after timely adjustment of doxycycline based drug treatment and active organ support. The lesions were completely absorbed without residual fibrous cord changes and the prognosis was good. Conclusions:Pneumonia caused by C. psitttaci usually presents sepsis, and the disease progresses rapidly. The mNGS is of value for the early diagnosis of C. psitttaci pneumonia. Timely adjustment of antibiotics treatment after etiological diagnosis can lead to a good prognosis.