This study aimed to investigate the effect of high hydrostatic pressure (HHP) on the physicochemical characteristics of blended low-protein wheat (LW) and oat flour. Additionally, quality changes in noodles made from blends treated with HHP were investigated. Crude protein and fiber contents of LW were not affected by HHP; however, those of blends were significantly higher than those of LW (p < 0.05). Water-holding capacity (WHC) of blends increased with HHP treatment. The peak viscosity of LW did not differ significantly because of HHP, and the peak and final viscosities of blends increased upon oat flour addition. The hardness, gumminess, chewiness of noodles made using LW improved with the addition of oat flour combined with HHP. The results indicated that the use of blends containing LW and oat flour as well as HHP treatment improved the quality and properties of noodles made using LW.