Fanconi anemia (FA) develops due to a mutation in one of the FANC genes that are involved in the repair of interstrand crosslinks (ICLs). FANCG, a member of the FA core complex, is essential for ICL repair. Previous FANCG-deficient mouse models were generated with drug-based selection cassettes in mixed mice backgrounds, leading to a disparity in the interpretation of genotype-related phenotype. We created aFancg-KO (KO) mouse model using CRISPR/Cas9 to exclude these confounders. The entireFancglocus was targeted and maintained on the immunological well-characterized C57BL/6J background. The intercrossing of heterozygous mice resulted in sub-Mendelian numbers of homozygous mice, suggesting the loss of FANCG can be embryonically lethal. KO mice displayed infertility and hypogonadism, but no other developmental problems. Bone marrow analysis revealed a defect in various hematopoietic stem and progenitor subsets with a bias towards myelopoiesis. Cell lines derived fromFancg-KO mice were hypersensitive to the crosslinking agents cisplatin and Mitomycin C, andFancg-KO mouse embryonic fibroblasts (MEFs) displayed increased γ-H2AX upon cisplatin treatment. The reconstitution of these MEFs withFancgcDNA corrected for the ICL hypersensitivity. This project provides a new, genetically, and immunologically well-definedFancg-KO mouse model for further in vivo and in vitro studies on FANCG and ICL repair.