This study was designed to evaluate the effect of thioglycol in extender on post-thaw quality of Nili-Ravi buffalo (Bubalus bubalis) bull spermatozoa. Semen from three buffalo bulls was collected at weekly intervals (three replicates; two ejaculates per bull per replicate) and qualifying ejaculates (n=18) were cryopreserved in extenders containing thioglycol at 0.0 or 0.5 or 1.0mM. Sperm motility (%; visually), plasma membrane integrity, (%;supravital hypo-osmotic swelling test), viability (%;dual staining technique using Trypan blue and Giemsa stains) and DNA integrity (%;acridine orange test) was assessed at 0, 2 and 4 hour post-thaw. Sperm motility, plasma membrane integrity and viability of buffalo bull spermatozoa were improved in a dose dependent manner with the supplementation of thioglycol at 0.5 mM and 1.0mM compared control. Sperm DNA integrity was similar (P>0.05) in extenders containing 0.5 mM and 1 mM thioglycol that remained higher (P < 0.05) than the values of DNA integrity in control. It is concluded that 1.0mM thioglycol in extender improved the motility, plasma membrane integrity, viability and DNA integrity of buffalo bull spermatozoa.