Plasma samples were collected from healthy as well as clinical and sub-clinical mastitis affected cows from Barasat, West Bengal, India. Plasma samples, after ammonium sulphate precipitation, were dialyzed against several changes of PBS (pH 7.2) to remove the excess ammonium sulphate. Then plasma fibrinogens were purified by gel filtration chromatography on Sephacryl S-200 HR. SDS-PAGE (10%) of purified fibrinogen from plasma of healthy cow revealed polypeptide bands of 74, 67 and 57 kDa which represent the α (alpha), β (beta) and γ (gamma)- chains respectively. On the other hand, purified fibrinogen from plasma of sub-clinical and clinical mastitis affected cow revealed polypeptide bands of 73 (α-chain), 68 kDa (β-chain) and 72 (γ-chain), 68 kDa (β-chain) respectively. The SDS-PAGE analysis showed the absence of gamma (γ)- chain of fibrinogen in both the samples of sub-clinical and clinical mastitis positive cow. Single precipitin line was observed in double immunodiffusion test when purified fibrinogen from healthy, clinical and subclinical mastitis positive cows reacted with hyper immune sera raised in rabbit. No precipitin line was found against the normal control serum. These purified fibrinogens also showed cross reactivity against antibody raised in rabbit when analyzed by western blot technique.