: Anxiety is a feeling of discomfort produced in face of an unknown event, as an impending cardiac surgery, that can lead to inconveniences in the intervention and subsequent recovery. Being the purpose of this research to analyze pre-surgical anxiety, a descriptive cross-sectional study among patients undergoing cardiac surgery was carried out. Data about sociodemographic variables were collected and the level of anxiety prior to surgery was assessed using the STAI-S scale. Subsequently, descriptive data analyses were performed, relationships among variables were analyzed, and a binary logistic regression model was developed in order to analyze the role of the variables involved in the development of preoperative anxiety. Sixty subjects were finally included; more than 80% had a moderate to high level of anxiety. 26.7% underwent valve surgery and 47% underwent coronary artery bypass graft (CABG) surgery, in the latter case presenting higher levels of anxiety. Statistically significant relationships were found among the level of anxiety and (a) level of studies, (b) first surgical intervention, and (c) the rating given to their previous surgical experience. We concluded that preoperative anxiety in people undergoing cardiac surgery is high and yet it is an underestimated phenomenon. The relationship between the received information and their anxiety level is inversely proportional, so that people programmed for cardiac surgery should be provided with all the information they required, through an individualized intervention.