Cryopreservation process reduces lipids and phospholipids from buffalo bull spermatozoa. It was therefore hypothesized that supplementation of fatty acid to extender may improve the post-thaw quality of buffalo semen. The objective was to evaluate the effect of arachidic acid supplementation in extender on post-thaw quality of buffalo bull (Bubalus bubalis) spermatozoa. Semen was collected from three adult Nili-Ravi buffalo bulls of similar age group with artificial vagina (42°C) for 3 weeks (replicate). Qualified semen ejaculates (n = 18) were split into four aliquots and diluted in tris-citric acid extender containing 0.0 (control), 5.0, 10.0 and 20.0 ng/ml at 37°C having approximately 50 × 10(6) spermatozoa/ml. Diluted semen was cooled to 4°C in 2 h and equilibrated for 4 h at 4°C. Cooled semen was filled in 0.5-ml straws at 4°C, kept on liquid nitrogen vapours for 10 min and plunged in liquid nitrogen for storage. Thawing of frozen semen was performed after 24 h at 37°C for 30 s. Sperm progressive motility (%) was improved in a dose-dependent manner by supplementing arachidic acid at 5.0, 10.0 and 20.0 ng/ml compared with control. Structural and functional integrity of sperm plasma membrane (%), number of acrosome-intact live sperm (%) and sperm chromatin integrity (%) were better (p < 0.05) in extender having 5.0 ng/ml of arachidic acid compared with control. At 10.0 ng/ml, these values did not vary (p > 0.05) from those at 5.0 ng/ml. Further improvement in structural and functional integrity of sperm plasma membrane, number of acrosome-intact live sperm and chromatin integrity was observed at 20.0 ng/ml of arachidic acid in extender. In conclusion, arachidic acid supplementation in extender improved the post-thaw quality parameters of cryopreserved Nili-Ravi buffalo bull spermatozoa. Among the arachidic acid concentrations studied, maximum improvement in post-thaw semen quality parameters was observed at 20.0 ng/ml.