The aim of this pilot study is to determine the feasibility and preliminary effectiveness of an individually designed preoperative therapeutic exercise program (PreTEP), in patients recently diagnosed with cancer and awaiting elective surgery. The purpose is to improve their physical fitness levels during this waiting period with the intention of decreasing postoperative morbidity. A preexperimental pilot study was performed at the University Medical Center Utrecht, The Netherlands. Thirty-nine patients diagnosed with cancer, scheduled for elective abdominal/thoracic surgery, were referred to a multidisciplinary preoperative screening. Fifteen patients (38%) participated in PreTEP. Participants were satisfied and motivated during the period of training (on average 5 weeks) in which they attended 84% of the sessions. Cardiorespiratory fitness (A strand-test) and muscle strength (Handheld Dynamometry) increased significantly, from 25 to 33 mL/kg/min, respectively (p<0.01; 95% confidence interval [CI]=-0.011 to -0.004) and from 894 Newton (N) to 961N (p<0.01; 95% CI=-94.53 to -39.0). No adverse events occurred during the training period. PreTEP was shown to be feasible, safe, and well-tolerated and appreciated by participants. Despite the relatively short period of training, physical fitness improved in all participants.