The aim of this study was to assay supplementation of cysteine into the traditional egg yolk extender for cryopreservation of buck spermatozoa. Semen ejaculates were collected from three fertile baladie bucks, aged 2.0 - 3years using artificial vagina. Collected semen was divided into four aliquots; the first was diluted with Tris-egg yolk extender without any supplementation (control), while the others were diluted with Tris-egg yolk extender supplemented with cysteine at levels of 0.5, 2.5 and 5mM. Semen diluted at a rate of 1:4 and placed into a refrigerator at 5oC for 4 h to equilibrate. At the end of equilibration period, extended semen was packaged in 0.25ml French straws and stored at –196oC. Thereafter, frozen semen was thawed by dipping the straws into a water bath at 37oC for 30 seconds. Percentages of progressive motility, live sperm, sperm abnormalities, plasma membrane and acrosome integrity were evaluated post dilution, equilibration period and postthawing of goat semen. The results revealed that there were a significant differences (P<0.05)of the percentages of sperm motility, live spermatozoa, sperm abnormalities and plasma membrane and acrosome integrity among post-dilution, post equilibration and post thawing of buck semen. Treatment supplemented with 2.5mM of cysteine led to significantly (P<0.05) improve the percentages of progressive motility, live spermatozoa, sperm abnormalities and plasma membrane and acrosome integrity of buck spermatozoa during different stages of cryopreservation compared to control and other levels of cysteine addition. In conclusion, supplementation of based Tris-egg yolk extender with 2.5mM of cysteine improves the percentages of progressive motility, live spermatozoa, sperm abnormalities and plasma membrane and acrosome integrity of frozen–thawed buck spermatozoa.