Wheat (Triticumspp.) yield is increased by either producing and testing variants of yield‐limiting genes or crossing to create new allelic combinations. Tiller number and seeds per tiller influence wheat yield, and both are impacted by the Teosinte Branched1(TB1) gene. We screened 16 hard red spring wheat (Triticum aestivumL.) cultivars, 15 hard red winter wheat cultivars and lines, and 10 durum wheat [Triticum turgidumL. subsp. durum(Desf.) van Slageren] cultivars and lines commonly grown in Montana and found several previously reported TB1missense alleles along with one new silent and a missense TB1‐A1allele among the 16 hard red spring wheat cultivars but no TB1null alleles. Among the 10 durum cultivars, five carried a TB1‐B1‐S184Gmissense allele and all winter wheat cultivars carried wild‐type TB1alleles. To determine the impact of TB1null alleles, this study examined durum wheat genotypes varying for TB1null alleles created by ethyl methanesulfonate (EMS) mutagenesis. The goal was to determine the impact of TB1null alleles on tillering, agronomic, and seed traits. The impact of TB1null alleles was studied alone and together in field trials. The TB1single‐ and double‐null mutants produced up to 15% more tillers and 18% with positive trends toward increased plant biomass. The results of this research demonstrate that the integration of EMS‐derived TB1null alleles may prove useful in increasing small‐grain tillering to optimize plant biomass and yield under different growing conditions. Teosinte Branched1null alleles increase wheat tillering.Selection for increased tillering can increase wheat biomass.Teosinte Branched1null impact is influenced by the environment.