Background and PurposePulmonary arterial hypertension (PAH) is a pulmonary vasculature obstructive disease that leads to right heart failure and death. Maresin 1 is an endogenous lipid mediator known to promote inflammation resolution. However, the effect of Maresin 1 on PAH remains unclear.Experimental ApproachThe serum Maresin 1 concentration was assessed using UPLC. A mouse model of PAH was established by combining the Sugen 5416 injection and hypoxia exposure. After treatment with Maresin 1, the right ventricular systolic pressure (RVSP) and right ventricular function were measured by haemodynamic measurement and echocardiography, respectively. Vascular remodelling was evaluated by histological staining. Confocal microscopy and western blot were used to test related protein expression. In vitro cell migration, proliferation and apoptosis assays were performed in primary rat pulmonary artery smooth muscle cells (PASMCs). Western blotting and siRNA transfection were used to clarify the mechanism of Maresin 1.Key ResultsEndogenous serum Maresin 1 was decreased in PAH patients and mice. Maresin 1 treatment decreased RVSP and attenuated right ventricular dysfunction (RVD) in the murine PAH model. Maresin 1 reversed abnormal changes in pulmonary vascular remodelling, attenuating endothelial to mesenchymal transformation and enhancing apoptosis of α‐SMA positive cells. Furthermore, Maresin 1 inhibited PASMC proliferation and promoted apoptosis by inhibiting STAT, AKT, ERK, and FoxO1 phosphorylation via LGR6.Conclusion and ImplicationsMaresin 1 improved abnormal pulmonary vascular remodelling and right ventricular dysfunction in PAH mice, targeting aberrant PASMC proliferation. This suggests Maresin 1 may have a potent therapeutic effect in vascular disease.