Neointimal hyperplasia remains an obstacle after vascular interventions. Programmed death‐1 (PD‐1) antibody treatment decreases tumor cell proliferation and secretion of inflammatory factors, and several antineoplastic drugs show efficacy against neointimal hyperplasia. We hypothesized that inhibition of PD‐1 inhibits neointimal hyperplasia in a rat patch angioplasty model. In a rat aorta patch angioplasty model, four groups were compared: the control group without treatment, a single dose of humanized PD‐1 antibody (4 mg/kg) injected immediately after patch angioplasty, PD‐1 antibody‐coated patches, and BMS‐1 (PD‐1 inhibitor)‐coated patches. Patches were harvested (Day 14) and analyzed. After patch angioplasty, PD‐1‐positive cells were present. Inhibition of PD‐1 using both intraperitoneal injection of humanized PD1 antibody as well as using patches coated with humanized PD1 antibody significantly decreased neointimal thickness (p = 0.0199). There were significantly fewer PD‐1 (p = 0.0148), CD3 (p = 0.0072), CD68 (p = 0.0001), CD45 (p = 0.001), and PCNA (p < 0.0001)‐positive cells, and PCNA/α‐actin dual positive cells (p = 0.0005), in the treated groups. Patches coated with BMS‐1 showed similarly decreased neointimal thickness and accumulation of inflammatory cells. Inhibition of PD‐1 using PD‐1 antibody or its inhibitor BMS‐1 can significantly decrease neointimal thickness in vascular patches. Inhibition of the PD‐1 pathway may be a promising therapeutic strategy to inhibit neointimal hyperplasia.