The physicochemical characteristics of fresh noodles made with blends of low-protein wheat flour and barley byproduct (BBP, 250 μm) were investigated. The crude protein contents (PC) of flour from Goso and Backjoong cultivars were 7.91% and 7.67%, respectively. PC and β-glucan contents from the BBP were 14.10% and 3.11%, respectively, which were higher than those in wheat flour. The water-holding capacity (WHC) of various blends was increased as a function of BBP but not gluten contents. Goso flour had the highest starch content (78.68%), with peak and final viscosities of 3,099 and 3,563 cp, respectively. Peak and final viscosities, trough, breakdown, and setback of the blends were decreased with the addition of BBP. Noodles made with Backjoong had the highest thickness score, while the hardness of noodles made with blends of Goso or Backjoong and 20% BBP were similar to those made from wheat flour only. The WHC of the samples was strongly correlated with PC, crude fiber, and β-glucan. The PC was not correlated with final viscosity, setback, thickness, hardness, gumminess, or chewiness.