Background Cardiac tamponade (CT) is characterized by compression of the cardiac chambers due to pericardial fluid accumulation. The etiology and prognosis may vary in different regions, and thus patient series from various regions can be useful for exploring the etiological and prognostic disparities. The aim of this study was to determine the clinical characteristics of patients with imminent CT, to evaluate the diagnostic performance of biochemical, microbiologic, and pathologic laboratory analysis, and to ascertain the prognosis of CT patients. Methods We enrolled all patients with imminent CT who underwent percutaneous pericardiocentesis between July 2012 and December 2017 in this retrospective study. The patients were classified into three etiology groups: (a) malignancy (MRCT); (b) iatrogenic/mechanical complication of myocardial infarction (IMCT); and (c) other causes (OCT). Clinical information, laboratory findings, and survival data were recorded. Results In total, 186 pericardiocentesis procedures were performed on 153 consecutive patients with CT. The median follow-up was 137 days (range: 1-1937). The MRCT group had the highest mortality rate (79%) in 12 months, while the OCT group had the lowest rate (27%). We determined that increased age, higher serum urea levels, and malignancy-related CT were independent predictors of mortality. The mortality rates of the MRCT and IMCT groups were similar, with both of them being significantly higher than the rate of the OCT group. In all, 15 patients were diagnosed with a new malignancy via pericardial fluid cytology. Conclusion Patients in the MRCT and IMCT groups had a poor prognosis. The presence of malignancy was found to be the most powerful predictor of mortality in CT patients.