Antigenic cross-reactivity among different helminths is the major challenge in developing a reliable tool for immuno-diagnosis and immuno-prophylaxis of parasitic diseases. The present study was designed to characterize the crude somatic antigen (CSAg) of Haemonchus contortus (CSAg-Hc) and Bunostomum trigonocephalum (CSAg-Bt) of sheep with a view to detect shared / cross-reacting polypeptides between these two nematodes. The study was performed by sodium-dodecyl-polyacrilamide gel electrophoresis (SDS-PAGE) and western blot analysis using homologous and heterologous hyper-immune sera (HIS) raised in rabbits against CSAg-Hc and CSAg-Bt separately. Six out of 10 polypeptides in CSAg-Hc and six out of 13 polypeptides in CSAg-Bt were found dominant by SDS-PAGE. Four polypeptides (Mw; 78, 68, 54, 37 kDa) out of seven immune-reactive polypeptides in CSAg-Hc and four polypeptides (Mw; 78, 68, 47, 29 kDa) out of nine immunogenic polypeptides were detected as immune-dominant by western blot analysis using homologous anti-sera. Four immunogenic polypeptides (Mw; 78, 68, 60, 37 kDa) were shared between these two nematodes as detected by SDS-PAGE and subsequently by immunoblot assay. One polypeptide (54 kDa) of CSAg-Hc and one polypeptide (55 kDa) of CSAg-Bt besides those four shared polypeptides showed cross-reactivity with HIS against CSAg-Bt and antiserum of CSAg-Hc, respectively. Two shared polypeptides (78 and 68 kDa) were observed as dominant immune-reactive polypeptides for both the parasites. The shared dominant immune-reactive polypeptides as identified in this study would ideally constitute promising candidate antigen for diagnosis of mixed infection of these two haematophagous nematode species.