Hospital readmissions are critical phenomena that delay the return of patients to their activities that maintain life, health and well-being. Objective:To assess the incidence and causes of readmission after hospital discharge in patients undergoing cardiac surgery. Method:Prospective observational study. The study included 181 patients who underwent cardiac surgery and were observed in the immediate preoperative periods and after hospital discharge on the 7th, 15th and 30th, through telephone contacts.Results:Of the 181 participants included in the study, 13 were discontinued due to intrahospital death and 1 due to transfer to another institution. Therefore, telephone contact was made with 167 patients, among whom 16 (9.58%) were readmitted. Of these, 2 were readmitted 7 days after hospital discharge; 7 were readmitted 15 days after discharge; and 7 readmitted 30 days after hospital discharge, with most readmissions due to infection of the surgical site in the mediastinum (18.75%) and saphenous vein (18.75%). Conclusion:Most readmissions were due to infection of the surgical site. This means that strategies to control and minimize these events should be part of the follow-up of cardiac surgery patients.