Mitochondria undergo fission and fusion to maintain homeostasis, and tumors exhibit the dysregulation of mitochondrial dynamics. We recently demonstrated that ectopic HRasG12V promotes mitochondrial fragmentation and tumor growth through Erk phosphorylation of the mitochondrial fission GTPase Dynamin-related protein 1 (Drp1). However, the role of Drp1 in the setting of endogenous oncogenic KRas remains unknown. Here, we show that Drp1 is required for KRas-driven anchorage-independent growth in fibroblasts and patient-derived pancreatic cancer cell lines, and it promotes glycolytic flux, in part through the regulation of hexokinase 2 (HK2). Furthermore, Drp1 deletion imparts a significant survival advantage in a model of KRas-driven pancreatic cancer, and tumors exhibit a strong selective pressure against complete Drp1 deletion. Rare tumors that arise in the absence of Drp1 have restored glycolysis but exhibit defective mitochondrial metabolism. This work demonstrates that Drp1 plays dual roles in KRas-driven tumor growth: supporting both glycolysis and mitochondrial function through independent mechanisms. Display omitted •Drp1 is required for oncogenic KRas-driven transformation•Drp1 promotes KRas-driven glycolysis•Loss of Drp1 inhibits pancreatic tumorigenesis•Loss of Drp1 impairs mitochondrial metabolism in tumor cells Nagdas et al. find that the mitochondrial fission GTPase Drp1 is required for KRas-driven transformation and pancreatic tumor growth. The inhibition of Drp1 in cells expressing oncogenic KRas leads to impaired glycolytic flux and the eventual loss of mitochondrial metabolic function.