Background: an increasing number of advanced age patients are considered for cardiothoracic surgeries. Prehabilitation optimizes the patients’ functional capacity and physiological reserve. However, the effectiveness of prehabilitation on physical functioning and postoperative recovery in the scope of cardiothoracic surgery is still uncertain. Objective: to assess the effectiveness of prehabilitation on pre- and/or postoperative functional capacity and physiological reserve in aged patients that are considered for cardiothoracic surgeries. Methods: this systematic review was registered in PROSPERO (CRD42021247117). The searches were conducted in PubMed, Web of Science, Scopus, and Cochrane CENTRAL until 18 April 2021. Randomized clinical trials that compared different prehabilitation strategies with usual care on the pre- and-postoperative results in aged patients undergoing cardiothoracic surgeries were included. Methodological quality was assessed by means of the Jadad scale, and the effectiveness of the interventions according to the Consensus on Therapeutic Exercise Training. Results: nine studies with 876 participants aged from 64 to 71.5 years old were included. Risk of bias was moderate due to the absence of double-blinding. The content of the interventions (multimodal prehabilitation n = 3; based on physical exercises n = 6) and the result measures presented wide variation, which hindered comparison across the studies. In general, the trials with better therapeutic quality (n = 6) reported more significant improvements in physical functioning, cardiorespiratory capacity, and in the postoperative results in the participants under-going prehabilitation. Conclusions: prehabilitation seems to improve functional capacity and postoperative recovery in aged patients undergoing cardiothoracic surgeries. However, due to the significant heterogeneity and questionable quality of the trials, both the effectiveness of prehabilitation and the optimum content are still to be determined.