Abstract- Background: Chronic kidney disease (CKD) is an independent risk factor and caused high morbidity and mortality for coronary artery disease (CAD). Several scoring systems can be used in assessing the severity of CAD, one of which is using the SYNTAX score (SXscore). Smoking is one of the risk factors for the progression of CAD and CKD. Several observational studies have under-reported the smoking factor influencing the relationship between eGFR and SXscore. Methods: This research is an observational study with a cross-sectional approach conducted at the Wahidin Sudirohusodo Hospital Makassar from July-August 2020. This study involved 62 CAD and CKD patients undergoing angiography. The estimated glomerular filtration rate was based on chronic kidney disease epidemiology collaboration (CKD-EPI)Coronary angiography results were converted to SXscore and smoking grade based on the Brinkman index. Results: This study involved 62 CAD and CKD patients male (71%), aged ≥ 55 years (77.4%), hypertension (71%), diabetes (35.5%), smoking (50%), eGFR G3a & G3b (53.9. %) and SXscore medium-high (50%). The results showed that lower eGFR could increase the SXscore (p < 0.001), especially in smoking subjects (p < 0.001). Multivariate analysis showed that gender was the most significant factor contributing to the relationship between eGFR and SXscore Conclusion : The lower eGFR could increase the SXscore, where this correlation was more significant in smoking patients. Multivariate analysis showed that gender was the most significant factor contributing to the relationship between eGFR and SXscore.