Purpose: To investigate the safety of and adherence to a prehabilitation program among patients with endometrial cancer and to provide preliminary evidence of the program’s efficacy in terms of health-related fitness (HRF) and patient-reported outcomes. Methods: Nineteen patients with endometrial cancer were recruited in a 2-week trial for a one-on-one supervised exercise program. All patients participated in an individual exercise program—the Challenge, Overcome, Resolve, and Enhance (CORE) program—which consisted of 60 minutes of moderate-to-vigorous intensity resistance, core stability, and aerobic exercise, supervised five times within 2 weeks before surgery. Results: Seventeen (89.5%) of the 19 participants completed the CORE program, and no adverse events occurred. All participants accomplished the daily mean step counts and sustained the prescribed target heart rate (reserve 50%–60%) during the CORE program sessions. Participants who completed the exercise program exhibited significantly improved HRF (cardiorespiratory fitness, 30-second chair stand, hand grip strength, curl-ups, sit and reach, single-leg standing with closed eyes; p<0.001 for all) without changes in the body mass index (p=0.113). Their quality of life (general, p=0.001; function, p=0.001; symptom, p=0.003), symptom clusters (p=0.006), anxiety (p<0.001), and depression (p<0.001) were significantly improved. Conclusion: The 2-week prehabilitation CORE program is safe and feasible for patients scheduled to undergo surgery for early-stage endometrial cancer and may improve their physical and psychological health status.