In addition to the loss of shattering and glume tenacity, wheat domestication was accompanied by changes in grain dimensions and an increase in grain size. Selection for grain dimension traits is likely associated with their correlation with yield, treatability, and grain milling properties. Our results indicate that the knock-out of TaGW7 results in shorter and wider grains, increased grain weight, and shorter plants. GW7 is a potential target of domestication as TaGW7-A1 falls into a domestication selective sweep region on chromosome 2A. The GW7-A1 alleles in hexaploid wheat and domesticated emmer wheat have a 1.9 kb insertion in the promoter region, which is present only in part of the wild emmer wheat accessions. The decreased expression of TtGW7-A1 in wild emmer is associated with the 1.9 kb insertion, and the expression of GW7-A1 in domesticated emmer is lower than in wild emmer. To investigate the phenotypic effects of the 1.9 kb insertion, the TaGW7-A1 allele from wheat cultivar Bobwhite was introgressed into wild emmer, and the allele from wild emmer was also introgressed into the Bobwhite cultivar. The introgression from Bobwhite into wild emmer did not result in shorter plants, or shorter and wider grains as expected, which suggests that wild emmer has other allelic variants of genes in the pathways that effect these phenotypes. Bobwhite plants with the TtGW7 allele without insertion had longer grains than the Bobwhite plants. These results suggest that GW7 is one of the domestication genes that contributed to plant height and grain dimension traits of cultivated forms of wheat.