A study was undertaken on semen of 3 Gir and 3 Murrah bulls to assess the effect of different concentration of antioxidant Sericin (0.10, 0.25, 0.50 and 1.00 %, w/v) in tris fructose yolk glycerol (TFYG) extender for improving its cryopreservation. Ejaculates with >70% initial motility were split- diluted @ 100×106 sperm ml-1 with extender without and with Sericin, and were soon evaluated for sperm quality parameters, viz., progressive sperm motility, morphology, viability, intact acrosome and HOS test. The split-diluted samples were then filled in French mini straws, equilibrated for 4 hrs at 4°C and frozen in liquid nitrogen vapour using a programmable bio-freezer. Straws thawed were again evaluated for post-thaw quality parameters including post-thaw incubation survival at 37°C for 3 hr in water bath. The mean progressively motile spermatozoa observed, irrespective of Sericin levels, on dilution, at pre-freeze and post-thaw stage in Gir bull semen were 76.93±0.39, 59.90±0.47 and 43.47±0.58 %, and in Murrah bull 78.20±0.38, 60.67±0.43 and 44.10±0.48 %, respectively. The mean values on dilution and at post-thaw stage for live sperm were 80.19±0.32 and 48.41±0.59 % in Gir, and 81.08±0.32 and 48.59±0.46 % in Murrah bull semen; total abnormal sperm 6.34±0.16 and 11.55±0.14 % in Gir and 6.64±0.12 and 11.27±0.13 % in Murrah bull semen; intact acrosome 89.86±0.20 and 82.58±0.23 % in Gir and 92.30±0.19 and 85.13±0.18 % in Murrah, and HOS reactive sperm 71.19±0.45 and 39.56±0.57 % in Gir and 71.62±0.42 and 39.33±0.54 % in Murrah bull semen, respectively. The mean progressively motile sperm observed after 1, 2 and 3 hrs of post-thaw incubation of semen at 37°C were 30.13±0.48, 19.63±0.42 and 10.77±0.40 % (p<0.001) in Gir, and 30.67±0.39, 20.70±0.37 and 12.20±0.31 % (p<0.001) in Murrah bull semen, respectively. The mean values of all above traits observed on dilution and at post-thaw stage/post-thaw incubation were significantly (p<0.05) better in TFYG extender with 0.50% and/or 0.25% Sericin than 0.10 or 1.00 % Sericin and control dilutor for both Gir and Murrah bull semen. It is concluded that inclusion of Sericin at 0.5% w/v in TFYG extender significantly improves post-thaw quality of bovine semen.