Primary meningococcal pericarditis (PMP) is a rare form of acute purulent pericarditis that often evolves into cardiac tamponade and usually requires pericardial drainage. PMP is a rare, difficult to diagnose, rapidly progressive form of meningococcal infections. PMP is typically caused by Neisseria meningitidis of serotype C, or, less commonly, B or W135. We report the second case of PMP caused by Neisseria meningitidis of serotype Y. Our patient was not critically ill at presentation, and her presentation could have been consistent with viral uncomplicated pericarditis with the exception of the mild leukocytosis with a left shift in the differential. Clinicians should be aware that early in the course of PMP, the illness may not be severe. Mild leukocytosis with a left shift or bandemia in the setting of what otherwise seems to be a case of uncomplicated viral pericarditis should prompt suspicion for PMP and further evaluation and/or monitoring.