Bacterial leaf streak (BLS) of wheat, caused by Xanthomonas translucens pv. undulosa, is an important disease of wheat worldwide. Use of resistant cultivars is the most preferred way of managing BLS. The objective of this research was to identify highly resistant wheat germplasm and map BLS resistance genes. Two collections of wheat germplasm, including triticale and spring wheat, were evaluated for their reactions to BLS. A wide range of reactions from highly resistant to highly susceptible were observed for both collections. Five triticale accessions and twenty-four spring wheat genotypes with high level of resistance to BLS were identified. Genome wide association studies using the spring wheat collection revealed seven quantitative trait loci on chromosomes 1A, 2B, 3B, 5A, 5B, 6A, and 7A significantly associated with BLS resistance. The identified resistant lines and molecular markers have a potential to be utilized in the breeding programs aiming to improve BLS resistance.