Low preoperative physical function in cancer patients is associated with postoperative complications; however, there have been no reports on the benefits of in-hospital preoperative rehabilitation on preoperative physical function in patients with pancreatic cancer. Therefore, the aim of this study was to quantitatively determine the effects of preoperative in-hospital rehabilitation provided under the supervision of a physiotherapist, on preoperative physical function in patients with pancreatic cancer. The study subjects were 26 patients (15 males, 11 females; age 71.2 ± 8.5 years, range: 51-87 years), including four patients with preoperative chemotherapy, scheduled for surgery for pancreatic cancer. Muscle strengthening exercises and aerobic exercises were conducted 11.9 ± 5.1 days prior to surgery. Cardiopulmonary exercise testing, 6-minute walk distance, and the Functional Independence Measure score were measured before and after the rehabilitation program. We also investigated the relation between the rehabilitation program and incidence of postoperative complications. All 26 study patients completed the preoperative rehabilitation program and no adverse events were noted. Peak oxygen uptake during cardiopulmonary exercise testing and 6-minute walk distance increased significantly after the rehabilitation program. The Functional Independence Measure score remained constant throughout the intervention. No wound infection, delirium, deep vein thrombosis, or respiratory complications were encountered postoperatively. In-hospital preoperative rehabilitation under the supervision of a physiotherapist significantly improved physical function and maintained physical activity in patients with pancreatic cancer. Such improvements may contribute toward preventing serious postoperative complications, resulting in better outcomes.