Sleep duration is an important determinant of cardiovascular health, yet the adverse effects of long sleep duration remain underexplored. While short sleep has well-documented associations with increased cardiovascular risk, emerging evidence highlights a U-shaped relationship, with excessive sleep also linked to adverse outcomes. This systematic review evaluates the association between prolonged sleep duration and cardiovascular health outcomes, including coronary artery disease (CAD), stroke, myocardial infarction (MI), hypertension, heart failure (HF), and atherosclerosis. A systematic search of PubMed, Embase, and Web of Science identified 38 studies published between 2008 and 2024 that investigated the relationship between sleep duration and cardiovascular health. Prolonged sleep duration was consistently associated with increased risks of CAD, stroke (ischemic and hemorrhagic), hypertension, and MI. Elevated inflammatory markers, such as C-reactive protein (CRP) and interleukin-6 (IL-6), emerged as potential mediators alongside demographic and lifestyle factors, including age, gender, and socioeconomic status. Long sleep duration may serve as a modifiable risk factor for cardiovascular diseases. Incorporating sleep assessments into cardiovascular risk evaluations could inform prevention strategies, and further research is needed to elucidate mechanisms and develop targeted interventions.