BACKGROUND: The Monocyte to High-Density Lipoprotein Ratio (MHR) ratio reflects the proatherogenic and antiatherogenic balance and increased MHR values are related to coronary atherosclerosis obstruction's presence, progressivity, and severity. This study uses medical records and coronary angiography data to assess the correlation between MHR and coronary artery diameter in coronary heart disease patients. METHODS: This study involved data from 230 patient medical records. The data collection approach was a cross-section design, and total sampling was performed by citing medical records of patients who underwent coronary angiography at the catheterization installation of Dr. Zainal Abidin Hospital, Banda Aceh, Indonesia. RESULTS: The multivariate test showed that MHR and the coronary slow flow group, MINOCA, and stenosis were significant with a value of  < 0.0001. The results of the bivariate test showed the relationship between MHR and coronary artery diameter in all three groups. Coronary slow flow, MINOCA, and stenosis were insignificant  > 0.05. CONCLUSION: This study shows that MHR can be a suitable, inexpensive, fast parameter for identifying the severity of coronary atherosclerosis obstruction.