Pulmonary arterial hypertension (PAH) is a chronic and progressive cardiopulmonary vascular disorder associated with poor clinical prognosis. Its hallmark pathological feature is sustained elevation of pulmonary vascular resistance resulting from extensive vascular remodeling. Endothelial-to-mesenchymal transition (EndMT), a critical event driving vascular remodeling, is increasingly recognized as central to PAH development and progression. This review systematically outlines the convergence of multiple pathophysiological insults on endothelial dysfunction and intimal remodeling in PAH, highlighting their roles in initiating EndMT. Principal factors include: (1) genetic and molecular alterations, such as BMPR2 mutations and epigenetic dysregulation; (2) environmental and toxic exposures, including chronic hypoxia and anorexigens; (3) inflammatory and immune dysregulation, exemplified by chronic inflammatory infiltrates and autoimmune conditions; and (4) hemodynamic and metabolic disturbances, notably aberrant shear stress and lipid metabolic imbalance. Given the critical contribution of EndMT to PAH pathogenesis, therapeutic strategies aimed at reversing EndMT represent promising anti-remodeling interventions. Preclinical studies have begun exploring EndMT-targeted therapies, including mesenchymal stem cell (MSC) transplantation and dipeptidyl peptidase-4 (DPP-4) inhibitors. Herein, we summarize recent advances regarding EndMT in PAH, dissect the molecular drivers and modulators initiating and sustaining EndMT, and critically evaluate emerging therapeutic strategies harnessing this pathway for clinical benefit.