Introduction: Cognitive factors such as individual perceptions and beliefs about their illness can play an important role in individuals adaptation style with their illness. The purpose of this study was to determine the predictors of illness perception in patients undergoing coronary artery bypass surgery (CABG). Methods: In this cross-sectional study, 217 patients who had CABG for over 6 months were selected by systematic random sampling method and by using a questionnaire consisting of two sections including socio-demographic and illness perception instrument. Data were analyzed using descriptive statistics and inferential statistics (Kruskal-Wallis and Mann-Whitney test). Also we used multiple logistic regressions for detecting predictor factors. Results: The mean age of samples was 58.70 ± 9.46. The majority of them were male (61.3%), married (83.4%),housewife (34.1%), The education level of majority was high school diploma (44.2%). The majority had desirable illness perception (93.5%). The mean score of total illness perception was 83.53 ± 5.96 and mean scores of its domain including cause, treatment and control, consequence and Timeline were 32.36 ± 3.6,28.07 ± 3.68,17.54 ± 2.26 and 5.57 ± 2.07,respectively. Multiple logistic regressions results showed about cause domain only monthly income (P<0.034, OR =0.290) and about treatment and control only age (P< 0.014,OR=2.217) were predictor factors. Conclusion: Fortunately in this study the majority of samples had desirable illness perception. Illness perception can affect the patients’ adaptation with their illness and their treatment adherence after CABG. Thus, interventions to promote understanding of the disease appear to be necessary.