In the southwestern part of Japan, weakness of the dough produced from soft wheat used for white salted noodles, resulting from low protein content and poor protein quality, is one of the shortcomings in noodle quality. We investigated the effect of the high-molecular-weight glutenin allele, Glu-D1d, on dough properties and noodle quality using near-isogenic lines (NILs) of three soft wheat cultivars. The NILs with the GluD1d allele showed significantly stronger dough, based on the sodium dodecyl sulfate sedimentation volume and the proportion of unextractable polymeric protein in total polymeric protein, than that of the corresponding recurrent parents with the Glu-D1f allele, suggesting that the Glu-D1d allele exerts a positive effect on dough strength, even when the protein content is low (around 8.0%). The positive effect of the Glu-D1d allele on dough strength was most pronounced in the cultivar harboring the Glu-A1c allele (null allele) with weaker dough. Significant differences were found between the NILs and the corresponding recurrent parents in the breaking force of cooked noodles based on instrumental assessment and in the noodle firmness based on sensory assessment, suggesting that the dough strength conferred by the Glu-D1d allele affected the firmness of cooked noodles.