Abstract Body: Coronary artery disease (CAD) is a heritable condition and the leading cause of mortality worldwide. Although effective therapies have contributed to a substantial reduction in CAD-related deaths over past decades, mortality rates have begun to rise in the most recent decade, coinciding with shifts in patient demographics. A CAD risk locus on chromosome 10q23 was identified through genome-wide association studies. Notably, this locus is not associated with established CAD risk factors such as hypertension, hyperlipidemia, or type II diabetes, providing an opportunity to uncover novel molecular pathways and therapeutic targets for CAD. In this study, we used improved fine-mapping methods to prioritize two lead noncoding single-nucleotide polymorphisms (SNPs), rs12260962 and rs17680741. Using chromatin accessibility assays, we found that rs12260962 resides within a plausible regulatory region specifically in endothelial cells (ECs), whereas rs17680741 lies within a putative enhancer in immune cells. Deletion of the region surrounding rs12260962 in ECs led to a decrease in TSPAN14 expression, while deletion of sequences surrounding rs17680741 had no effect in ECs. Consistently, enhancer activity assays demonstrated that in ECs, the 1 kb sequence surrounding rs12260962 enhanced reporter gene expression, whereas the sequence surrounding rs17680741 did not. To further elucidate the role of TSPAN14 in EC biology, we performed transcriptomic analyses in clonal TSPAN14 knockout ECs and found that TSPAN14 deficiency resulted in differential expression of genes involved in Notch signaling, heart morphogenesis, cell adhesion, and wound healing. Subsequent functional studies confirmed that TSPAN14 is required for full activation of NOTCH1-mediated signaling. In its absence, ECs exhibited disrupted cell–cell junctions, impaired repair capacity, and reduced mechanosensitivity. To our knowledge, this is the first study to link a disease risk variant to a direct regulator of Notch signaling in the context of CAD. Together, these findings define a genetically supported disease mechanism and provide a foundation for the development of targeted therapeutic strategies.