Pulmonary arterial hypertension (PAH) is a complex, progressive disease characterized by an increased mean pulmonary arterial pressure at rest, and is associated with a high rate of mortality due to right ventricular failure as the disease progresses. While numerous animal and cell culture models have been created in an attempt to better elucidate the disease mechanisms, these models fail to fully recapitulate the disease phenotype, thus severely hampering research and and drug development for PAH. This research aims to take some of the steps necessary to build a more physiologically and pathologically accurate tissue engineered in vitro heart model of PAH for improved drug screening and disease modeling of the right ventricle. Approaching the vascular aspect of such a model, we aimed to develop a method to differentiate induced pluripotent stem cells derived from PAH patients into functional endothelial cells, while also developing a framework for their incorporation into the engineered heart tissue model alongside PAH cardiomyocytes. Based on a literature review of endothelial differentiation methods, a novel differentiation protocol was designed and validated by exploring the quality of endothelial differentiation through gene, protein, and functional characterizations as compared to undifferentiated stem cells and primary endothelial cells. Investigation of their phenotype revealed that the differentiation protocol developed here effectively produces populations of immature PAH endothelial cells that replicate many of the attributes of mature primary endothelial cells, while preliminary work has demonstrated successful integration alongside cardiomyocytes into the engineered tissue matrix. While further research is still necessary to optimally vascularize the engineered tissues using these differentiated endothelial cells, this research marks the first time patient-derived PAH endothelial cells have been integrated into an engineered heart tissue model, moving a complete 3D model of PAH one step closer to reality.