Objective: During sleep, blood pressure (BP) is generally 10%–20% lower, and the risk of target organ damage in non-dip per hypertension (HT) is related to left ventricle hypertrophy, MI, and stroke. This study aimed to analyze the effect ofnon-dipper HT on the prevalence of coronary artery disease (CAD), time of symptom onset, and in-hospital MACE in pa tients with acute coronary syndrome (ACS). Materials and Methods: We included 107 patients who were diagnosed with ACS and had angina pectoris lasting 12 h atmost and no history of CAD in this study. Patients’ ambulatory BP was monitored for 24 h. Patients were divided into thenon-hipper and dipper groups according to the decrease in BP during nighttime. We compared the prevalence of CAD, timeof symptom onset, and in-hospital MACE in both groups. Results: We included 52 patients in the non-dipper group and 55 patients in the dipper group in this study. When wecompared the Syntax and Gensini scores between the groups, statistical significance was determined (p=0.006). In terms ofsymptom onset hours, 32 (62%) and 19 (35%) patients were admitted with night angina pectoris in the non-dipper and dip per groups, respectively (p=0.007). In terms of in-hospital MACE ratios, we identified MACE in six patients in the non-dippergroup and three patients in the dipper group (p=0.223). Conclusion: In our study, we conclude that non-dipper HT increases the number of lesions, MI cases at night, and MACEratios in CAD by causing endothelium dysfunction and stimulating thrombocyte activation.