ABSTRACT Gelatin as a high viscosity protein can reduce sperm metabolism by reducing sperm movement. So, this study was set out to examine the impact of adding gelatin to Tris-citric-egg yolk extender (0, 0.5, 1.0 and 1.5%) on visual sperm characteristics, CASA analysis parameters, total antioxidants capacity, and enzyme activity in in post-thawed ram semen. Total of 5 rams have been used for collecting semen once weekly for 5 weeks. Pooled semen was diluted with the different levels of gelatin, equilibrated at 5^oC for 4h and stored in liquid nitrogen. Semen had been evaluated post thawing. Results showed a positive effect of gelatin supplementation in extender on sperm characteristics, including progressive motility, livability, abnormality, and membrane integrity. Gelatin addition improved CASA -motility parameters and normality, while decreasing sperm velocity of sperm cells as well as increasing total antioxidant capacity and glutathione peroxidase, and decreasing enzyme activity (LDH) of post-thawed sperm medium. In conclusion, gelatin supplementation to Tris semen extender at a level of 1.5% is considered as a good enhancement on sperm function in post-thawed ram semen.