The hemagglutination assay is a simple and easy method to specify a lectin. An activelectinagglutinates erythrocytes by recognizing a carbohydrate on the cell surface and forming a cross-linked network in suspension. The assay is traditionally performed on a microtiter plate, where the lectin solution is serially diluted and the minimum concentration of a lectin causing agglutination is detected. The crude extract of Senna occidentalis and Sesbania bispinosa seedscontain considerable amount of protein. It was found that 10 gm of Sesbania bispinosaand Senna occidentalis seeds contain about 12.6 mg/mL and 9.8 mg/mL of protein and minimum agglutination concentration was found to be 0.393 mg/mL for Sesbania bispinosa in each group of human erythrocytes (A, B, O and AB) and 0.613 mg/mL for Senna occidentalis in chicken erythrocytes. Finally, the hemagglutination assay confirmed that possible lectins have been presented in the Sesbania bispinosa and Senna occidentalisplant sources.