The objective of this study was to investigate the effects of non essential amino acids solution (NESS) to freezing extender on standard qualitative semen parameters (motility, viability and acrosomal integrity), oxidative parameters (antioxidant enzymes activities and lipid peroxidation), ultrastructure alterations and in vitro fertilizing potentials of frozen-thawed ram semen. Ejaculate samples were collected with artificial vagina from five adult fertile rams and diluted with Tris-base extender containing non essential amino acids solution  (20, 50, 100 and 200µl/ml) or without amino acids (control). Diluted semen was cooled to 4^oC throughout one hour and frozen in 0.25 ml straws, prior to being stored in liquid nitrogen. Cryopresreved spermatozoa were assessed for post-thawing sperm motility, viability and acrosomal integrity, ultrastructure changes, antioxidant activities, lipid peroxidation and in vitro fertilizing potentials. The current results clearly indicated that adding 100µl/ml non essential amino acids to Tris extender significantly improved (P< 0.05) post-thawing motility, viability index and maintained acrosomal integrity (65.00± 2.89%, 169.16±5.46 and 12.67±1.2 %, respectively) compared with the control semen (50.00±7.16 %, 109.33± 8.37 and 21.66±3.38 %). Moreover, addition of 100µl/ml non essential amino acids to the semen extender significantly diminished (P< 0.05) the lipid peroxidation (11.91±1.76 nmol/ml) compared with the control semen (20.11±2.68 nmol/ml). Furthermore, the current results illustrated that addition of 100µl/ml non essential amino acids protected the plasma membrane, acrosomal region and mitochondria and maintained the ultrastructure integrity of the cryopresreved spermatozoa and DNA integrity compared with the control spermatozoa. All of these previously enhanced semen characteristics were reflected positively on its in vitro fertilizing capacity. Therefore, the present results revealed that addition of 100µl/ml non essential amino acids to the freezing extender might improve semen quality and reduce cryodamage of the ram spermatozoa.