BACKGROUND: Purulent pericarditis is a rare, life-threatening condition often caused by Streptococci, Staphylococci, Haemophilus species, or Mycobacterium tuberculosis. Coinfection cases are exceedingly uncommon. We aim to document and share this rare case through this case report. CASE PRESENTATION: We report the case of a 44-year-old woman with no significant past medical history who presented to the emergency department of Chang Gung Memorial Hospital, Linkou branch, at Taoyuan, Taiwan, in July 2024 with a 3-day history of chest discomfort, shortness of breath and fever. Imaging revealed pericardial and mediastinal fluid with gas. Pericardiocentesis drained the pericardial effusion and later identified Eikenella corrodens and Parvimonas micra via MALDI-TOF mass spectrometry. A history of fish bone impaction one month prior suggested an oral origin for the infection, although imaging revealed no esophageal perforation. The patient underwent pericardial drainage, video-assisted thoracoscopic surgery for abscess drainage, and four weeks of antibiotic treatment with ampicillin-sulbactam, leading to full recovery. CONCLUSION: To our knowledge, this is likely the first documented case of purulent pericarditis caused by Eikenella corrodens and Parvimonas micra simultaneously. This case highlights the importance of a multidisciplinary approach and prompt management, including drainage and tailored antibiotic therapy, in mitigating the high mortality associated with purulent pericarditis.