Objectives: The aim of this meta-analysis was to assess association between a composite clinical outcome (severe infection/ required ICU admission/ death) of COVID-19 pneumonia and demographic, clinical, laboratory and radiological findings of these patients. Methods: A literature search was conducted using the databases PubMed, Medline, Scopus and Web of Science till July. Relative risk (RRs), standardized mean difference (SMDs) and 95% confidence intervals (CIs) were pooled using random-effects models. We described overall estimates of relevant data of clinical importance from 116,260 COVID-19 pneumonia patients including 19,628 with composite end points from 40 observational studies of 5 countries. Results: The result showed that male gender (RR=1.24, p 64 years (RR=2.52, P <.001) followed aggravated course. Delayed hospitalization (SMD=.75, p= 0.005), presence of co-morbidity (RR= 1.76, p<.001) and multiple co-morbidities (RR=1.50, p<.001) were associated with higher risk of fatal course. Pooled data reported significantly high neutrophil-lymphocyte ratio (SMD=10.79, p<.001), low lymphocyte-to-C-reactive protein ratio (SMD=-3.89, p<.001), low platelet count (SMD=-1.622, p<.001), prolonged prothrombin time (SMD=0.98, p<.001), high lactate dehydrogenase (SMD=6.260, p<.001), D-dimer (SMD=1.92, p<.001), creatine kinase (SMD=1.68, p= 0.001) and interleukin-6 level (SMD=2.84, P=.001) in patients with fatal outcome. Funnel plots and Egger’s tests did not reveal any significant publication bias. Conclusions: Features like older age, male gender, presence of co-morbidities and delayed hospitalization along with the laboratory findings consistent with infection, immune system activation, coagulation disorder and tissue damage could help clinicians to identify COVID-19 patients with poor prognosis at an early stage. J Microbiol Infect Dis 2019; 9(3):121-135.