This study assessed functional health literacy and associated factors among adult patients with cardiovascular diseases (CVDs) in Ethiopia. Methods: A cross-sectional study was conducted on 410 respondents from May 1 to July 1, 2020, using a functional health literacy questionnaire consisting of 14 items that covers three conceptually distinct functional health literacy domains: having sufficient information to manage my health, ability to find good health information and understand health information well enough to know what to do. Data were analyzed using the Statistical Package for Social Sciences (SPSS) Version 23. Data were collected by exit face-to-face interview using an interviewer administered and pre-tested questionnaire. Statistical significance of associated variables had been declared based on the adjusted odds ratio (AOR) with its 95% CI and p-value <0.05. Results: Adequate functional health literacy was determined in 55.4% of CVD patients understanding health information whereas inadequate functional health literacy was determined in 53.9% participants for finding health information and in 50.5% of them having sufficient information to manage my health. Educational status was found to have a statistically significant association across the three domains. Conclusion:The functional health literacy level of CVD patients varied by domain. Educational status of the participant is significantly associated with the three domains of functional health literacy whereas household monthly income and number of information sources are significantly associated with having sufficient information and the ability to find good health information. The findings indicate the need to streamline medical communication that improves the functional health literacy of CVD patients.