IntroductionHemopneumopericardium defines a condition of combined pathology of weakened, dense blood content (hemopericardium) and air (pneumopericardium) in the pericardial cavity with an air fluid level. It is a rare disease, with only one such case reported in the literature. In this case report, we assessed a patient rectal cancer in addition to hemopneumopericardium, dyspnea, and chest pain.Clinical case reportA 47-year-old Arab woman previously diagnosed with rectal cancer metastasized to bones, lymph nodes, and lungs post-Hartmann procedure reported to the emergency department complaining of worsening dyspnea for 2 weeks, more significantly in the supine position. A productive cough with yellowish sputum characterized this; however, there was no pertinent family or psychological history. Examination of the respiratory system revealed dullness on the left side associated with decreased breath sound. The chest radiograph also revealed marked hydro-pneumopericardium. Spiral computed tomography angiography of pulmonary arteries demonstrated pericardial effusion with the air fluid level at pericardial space, implying hydro-pneumopericardium.Clinical conclusionA successful pericardiocentesis was performed, in which 180 cc of blood-filled pericardial fluid was drained, suggesting the presence of hemopneumopericardium. Hemopneumopericardium has multiple etiologies, yet critical intervention is restricted in patients with cardiac tamponade. Hence, pericardiocentesis could be a definitive treatment.