Purpose: To evaluate and correlate corneal endothelium parameters with the severity of primary glaucoma. Methods: This prospective case-control study was conducted on 150 eyes of 80 newly diagnosed primary open-angle glaucoma (POAG), chronic primary angle-closure glaucoma (cPACG), and normal-tension glaucoma (NTG) patients in a tertiary care center. Endothelial parameters including endothelial cell count (ECC), percentage of hexagonal cells, and coefficient of variation of cell size were analyzed. Glaucoma cases were further sub-grouped into early, moderate, and severe glaucoma and compared for endothelial parameters. Chi-square, Fischer’s exact test, independent sample t -test, and analysis of variance were performed using IBM ® SPSS ® Statistics version 28. Results: The ECC was markedly reduced in cases (2281 cells/mm 2 ) versus controls (2611 cells/mm 2 ) ( P < 0.001). The POAG (2251 cells/mm 2 ) and cPACG (2287 cells/mm 2 ) eyes had significantly a lower ECC compared to healthy controls ( P < 0.001), whereas NTG eyes had a lower mean ECC (2538 cells/mm 2 ), but it was not statistically significant ( P > 0.05) when compared with controls. The ECC decreased with an increase in severity as patients with early glaucoma had an ECC of 2284 cells/mm 2 , moderate 2261 cells/mm 2 , and severe 2086 cells/mm 2 , and the difference was statistically significant. Conclusion: A significant decrease in corneal ECC was observed in POAG and cPACG patients when compared with healthy controls of the same age group. Mechanical damage following an elevated intra-ocular pressure for a longer duration may be attributed to morphological and consequent functional damage to endothelial cells.