Identification of NAM-1 alleles associated with high grain protein content in wheat relatives has enhanced the significance of distant hybridization from the point of view of the nutritional value of T. aestivum L. grain. The effects of NAM-A1 and NAM-B1 allelic variations on grain protein content and productivity traits in 22 wheat lines with T. dicoccoides, T. dicoccum, T. spelta, and T. kiharаe genetic material and their parental forms under the field conditions of Belarus (2017-2021) were evaluated. Among the parental forms, the functional NAM-B1 allele (F) was identified only in the accessions of wheat relatives. All parental varieties and most introgressive lines (77.3%) had a non-functional allele (NF). Six combinations of NAM-A1/B1 alleles were identified in the investigated genotypes and their frequencies varied from 40% (d/NF) to 3% (c/NF). The cumulative contribution of NAM-A1 and NAM-B1 genes to the variability of economically important wheat traits ranged from 8-10% (grain weight per plant and thousand-kernel weight) up to 72% (grain protein content) according to two-way ANOVA. The proportion of variance determined by weather conditions was small (1.57-18.48%) for most investigated traits. The “NAM-A1/B1 × weather conditions” interaction determines 65-71% of the variance of wheat productivity traits, but it proves to be insignificant for the grain protein content. It was demonstrated that the presence of the functional NAM-B1 allele provides for a high level of protein accumulation in grain and does not lead to an essential decrease in thousand-kernel weight, irrespective of weather conditions. High yield parameters and protein accumulation level in grain were established for the genotypes, combining the NAM-A1d haplotype and the functional NAM-B1 allele. The results obtained demonstrate the effectiveness of the functional NAM-B1 allele introgression from relative species for enhancing grain wheat nutritional value.