The study was conducted to evaluate the effect of addition of L-cysteine to tris-citric acid (TCA) extender on the post-thaw quality of Sahiwal bull semen. For this purpose, two consecutive ejaculates were collected from three Sahiwal bulls using artificial vagina at weekly intervals for a period of three weeks (three replicates). Qualifying semen ejaculates were diluted (50×106 motile spermatozoa ml-1) in TCA extender having L-cysteine either 0.0 (control) or 0.5, 1.0 or 2.0 mM. Diluted semen was cooled to 4°C for 2 h, equilibrated for 4 h at 4°C, filled in straws at 4°C, kept in liquid nitrogen vapours for 10 min and then stored in the liquid nitrogen. Thawing was performed after 24 h of storage, at 37°C for 30 s. and the sperm motility, viability, plasma membrane and acrosomal integrity were assessed. Higher (P<0.05) sperm motility, viability, plasma membrane and acrosomal integrity were observed using extenders containing 1.0 or 2.0 mM compared to those containing 0.5 or 0.0 mM L-cysteine. It is concluded that addition of L-cysteine (to reach 1.0-2.0 mM) in TCA extender improves the post-thaw quality of Sahiwal bull semen.