Cardiovascular diseases are the leading cause of death globally, and nurses have a crucial role in informing cardiovascular disease patients about their diseases. The aim of the present study was to identify the effect of activities of daily living on the self-care agency of patients in a cardiovascular surgery clinic. This descriptive study was conducted between June 2014 and January 2015 with 180 patients hospitalized in the cardiovascular surgery clinic of a university hospital in the province of Erzincan in the Eastern region of Turkey. The data of the study were gathered using a descriptive form designed by the authors, Katz index of activities of daily living scale (ADLS), Lawton-Brody instrumental activities of daily living scale (IADLS), and self-care agency scale (SCAS). The data were processed using computer software and assessed using percentages, means, t test for independent groups, one-way analysis of variance, and correlation analysis tests. It was found that 50.6% of the patients were >= 65 years, 66.1% were male, 46.1% perceived their health status as moderate, and 35.6% had previously had heart attacks. The patients' mean ADLS score was 16.39 +/- 2.30, their mean IADLS score was 19.23 +/- 4.16, and their mean SCAS score was 92.11 +/- 18.81. The patients' education level and perceived health were found to affect their mean SCAS scores. In addition, there was a positive correlation between the patients' ADLS and IADLS scores and their SCAS score. It was also noted that patients were more independent on the ADL and IADL, and that their self-care agency was higher.