In this study, (17) pericardial effusion specimens and blood samples were obtained from hospitalized patients diagnosedwith pericardial effusion at Marjan Teaching Hospital, AL-Sader Teaching Hospital and Ibn-AL-Biatar Cardiovascular Center with age range between (2-77) years old from both sexes, 6(35.30%) male and 11(64.70%) of them were female. The period of collection were extended from July (2018) to January (2019). A total of (17) samples from hospitalized patients with pericardial effusion were included in this study, only 9(52.9%) patients with positive bacterial blood culture media, 7(77.8%) from female and 2(22.2%) from male, and 10(58.8%) patients with positive bacterial pericardial effusion, 7(70%) female and 3(30%) male. In the positive culture group, from 10(58.8%) cases, death occurred in 2(20%) patients, and in the negative culture group, from 7(41.2%) cases, death occurred in 2(38.5%) patients. The sera and pericardium effusion of patients in showed anti-IgM to M. pneumoniae, M. pneumophilia, L. pneumophilia, C. pneumophilia, RSV, Adenovirus, Influenza A virus, and Influenza B virus antibodies. The results showed 7/17(41.2%) positive cases of pericarditis attributed to M. pneumoniae. In (17) patients with acute pericarditis admitted found 2/17(11.8%) positive cases detected by IFA in patients with L. pneumophilia. IFA revealed that 1/17(5.9%) of positive cases for the assay positive for Chlamydophila pneumoniae. Recent study revealed that the IFA detect 2/17 (11.8%) of cases positive for Adenovirus. Depending on IFA recent study identified 2/17(11.8%) cases with RSV associated with another etiological agents and present a case of Influenza A virus infection 1/17(5.9%). Our results showed a case with pericardial effusion positive for Influenza B virus 1/17(5.9%) associated with presence of RSV and L. pneumophilia in patient with intestinal cancer with negative results of bacterial culture media for both pericardial effusion and blood.