<b><i>Background:</i></b> Malnutrition is a frequent finding in patients undergoing cancer surgery, especially in the elderly. The decreased nutritional status leads to increased complications and to delayed recovery after the surgical procedure. While established concepts of enhanced recovery after surgery and rehabilitation aim at improving the patient <i>after</i> surgery, the concept of prehabilitation is targeting the phase <i>before</i> surgery. This multimodal concept incorporates preoperative nutritional support. <b><i>Summary:</i></b> Nutritional conditioning targets an increase in the functional reserve preoperatively to optimize recovery in the postoperative period. Routinely, it is combined with an exercise program according to the patient’s state. Individualized meal plans help to meet the patient’s requirements and should start approximately 4 weeks prior to surgery. An important part of the nutritional conditioning is to guarantee a daily protein intake of at least 1.2 g/kg body weight. This may be realized by commercially available whey proteins in particular or milk proteins in general. <b><i>Key Messages:</i></b> All specialists involved in the care of cancer patients should recognize the care continuum that starts when the need for surgery is identified and aims at increasing the functional capacity throughout the pre-, peri- and postoperative phase by means of prehabilitation, enhanced recovery programs and rehabilitation.