BACKGROUND Bacterial pericarditis can present a diagnostic challenge due to the difficulty of obtaining tissue for bacterial identification. This report is of a 34-year-old man who presented with fever and cough. Diagnosis was initially delayed without a tissue sample, but the patient was later found to have polymicrobial bacterial pericarditis. CASE REPORT A 34-year-old man from the Democratic Republic of Congo presented to the emergency room with cough, fever, and night sweats. He was admitted and found to have pericardial thickening and fluid collection with calcifications. A tissue sample was not obtained for diagnosis, and he was discharged on RIPE (rifampin, isoniazid, pyrazinamide, and ethambutol) and steroids for presumed tuberculosis pericarditis. He worsened clinically and was readmitted to the hospital with evolving pericardial effusion with air present, in addition to new pleural effusion and parenchymal consolidation. He subsequently underwent thoracotomy and pericardial biopsy. Tissue cultures and sequence-based bacterial analysis eventually revealed the presence of Prevotella oris and Fusobacterium nucleatum. He improved dramatically with appropriate antibiotic therapy. CONCLUSIONS This report demonstrates the importance of undergoing further diagnostic work-up for bacterial pericarditis, especially in resource-rich settings. Although tuberculosis pericarditis should remain high on the differential, it is imperative not to anchor on that diagnosis. Instead, when feasible and safe, tissue biopsy should be obtained and sent for organism identification. AFB smears and cultures, Xpert MTB/RIF, and sequence-based bacterial analysis have all been used for identification. Delay in diagnosis can lead to progression of disease and unnecessary incorrect therapies.