Background <p>Psittacosis pneumonia is not uncommon, and it can progress to severe illness or even death. Identifying the clinical characteristics of <i>Chlamydia psittaci (C. psittaci</i> ) pneumonia and its risk factors were the aim of improving decision-making regarding diagnosis and treatment.</p> Methods <p>According to the guidelines for CAP, 59 patients with <i>C. psittaci</i> pneumonia were divided into a non-severe pneumonia group and a severe pneumonia group, and their clinical characteristics and the differences were analyzed and compared.</p> Results <p>The incidence of consciousness disorders is higher(<i>P</i> = 0.020), and the time from onset to diagnosis is longer (8 days vs. 14 days, <i>P</i> = 0.002), it is more prone to myocardial injury, kidney injury, hypoalbuminemia, coagulation abnormalities, and venous thrombosis (<i>P</i> &lt; 0.05) in the severe group, while fatigue is more common in the non-severe group (<i>P</i> = 0.022). On laboratory indicators, the severe pneumonia group had a significantly longer prothrombin time (<i>P</i> = 0.007), higher WBC and neutrophil percentages and lower lymphocyte count and percentages, higher lactate dehydrogenase and D-dimer values (all <i>P</i> &lt; 0.001). After adjustment for sex and age, logistic regression analysis identified myocardial injury as an independent risk factor for severe <i>C. psittaci</i> pneumonia (OR, 124.3, [95%CI, 4.25 ~ 3633.24]; <i>P</i> = 0.005).</p> Conclusions <p>Impaired consciousness indicates severe illness and myocardial injury is an independent risk factor for severe <i>C. psittaci</i> pneumonia.</p>