<p>Post-traumatic pericarditis is a subtype of post-cardiac injury syndrome (PCIS) that occurs after non-iatrogenic cardiac trauma. Post-traumatic pericarditis is rare and difficult to diagnose. We present a case of post-traumatic pericarditis progressing to transient constrictive pericarditis following a penetrating stab wound to both ventricles, illustrating the role of multimodal imaging in diagnosis and follow-up. A 22-year-old male presented with a two-day history of severe pleuritic chest pain, six weeks after surviving a penetrating stab injury to the left and right ventricles. Initial evaluation revealed no fever, a normal cardiovascular examination, and stable vital signs. Inflammatory markers were raised, and electrocardiography (ECG) showed anterolateral T-wave inversion without PR depression or ST elevation. CT pulmonary angiography demonstrated moderate pericardial effusion and mild pleural effusion. Echocardiography showed a small pericardial effusion with septal bounce, suggesting early constriction. Cardiac magnetic resonance imaging (MRI) demonstrated pericardial thickening, prominent septal bounce and flattening, and circumferential late gadolinium enhancement, in keeping with acute transient constrictive pericarditis. The patient was treated with colchicine, ibuprofen, and prednisolone. Serial follow-up MRI showed resolution of the pericardial inflammation. This case highlights post-traumatic pericarditis as a rare complication of life-threatening penetrating cardiac trauma. Serial multimodal imaging, particularly cardiac MRI, may support the diagnosis and help monitor the response to anti-inflammatory therapy.</p> Graphical abstract <p></p>