GPT is a conserved ER-resident transmembrane protein that catalyzes the initial step of protein N-glycosylation in vertebrates. However, to date, there have been no reports on GPT in silkworms. In the present study, we identified a GPT ortholog in the B. mori genome. Spatiotemporal expression profiles showed that BmGPT was highly expressed in the majority of silkworm's organs. BmGPT regulates multiple cellular processes such as cell viability, proliferation, and cell death. In addition, BmGPT overexpression increased BmNPV proliferation in BmN cells, whereas BmGPT inhibition by siRNA or a chemical inhibitor suppressed BmNPV proliferation both in vitro and in vivo. These results suggested that BmGPT facilitates BmNPV proliferation by regulating cell proliferation and apoptosis. This study identifies a potential molecular target for BmNPV prevention and for silkworm breeding.