Synthetic hexaploid (SH) wheat (AABBD’D’) is developed by artificially generating a fertile hybrid between tetraploid durum wheat (Triticum turgidum, AABB) and diploid wild goat grass (Aegilops tauschii, D’D’). Over three decades, CIMMYT has developed and utilized SH wheat to bridge for the gene transfer from Ae. tauschii and durum wheat to bread wheat and is a unique example of success utilizing wild relatives in mainstream breeding at large scale. Our study aimed to determine the genetic contribution of SH wheat to CIMMYT’s global spring bread wheat breeding program. We estimated the theoretical contribution of D’ to synthetic derivative lines using the ancestral pedigree and marker information. The average marker-estimated contribution was 17.5% and the marker-estimated contribution of D’ in the synthetic derivatives varied among segments in the genome. The results demonstrated diverse levels of selection pressure applied in a breeding program across all parts of the genome. The results of theoretical contribution of D’ based in two CIMMYT international yield trails consisting of 1,600 advanced lines showed that 20% of the lines were synthetic derived with an average D’ contribution of 15.6%. Our results underline the importance of SH wheat in maintaining and enhancing genetic diversity and genetic gain over years and implication of results to breeding program will be discussed.