The study aimed to evaluate the prognostic importance of small pericardial effusion (SPE) found on echocardiography in a cohort of patients hospitalized for acute ischemic stroke. We prospectively followed a series of 408 consecutive first-ever acute ischemic stroke patients aged ≥50 years who were admitted to the hospital within 24 h of the onset of stroke symptoms. All of the patients underwent transthoracic echocardiography within the first 48 h. Exclusion criteria were cardiothoracic surgery or acute myocardial infarction within the previous 6 months, a moderate or greater pericardial effusion (>1 cm if circumferential), and inadequate visualization of the pericardial space. The patients were followed for 1 year or until death, whichever came first. SPE was noted in 64 (15.7 %) of the patients. Mortality at 1 year was greater for patients with a small effusion (n = 21, 32.8 %) compared to those without an effusion (n = 40, 11.6 %, p < 0.001). After adjustment for age, demographics, medical history, and other echocardiographic findings, SPE remained associated with higher mortality (OR 2.515; 95 % CI 1.188-5.477; p = 0.008). This study is the first to demonstrate that the presence of SPE is associated with increased mortality in patients with first-ever acute ischemic stroke.