Agglutinins/lectins are conventionally defined as proteins/ glycoproteins of non-immune origin with a remarkable ability to specifically and reversibly interact with carbohydrate ligands. Lectins from different sources may essentially exhibit common biological activities. This study was therefore undertaken to survey naturally occurring agglutinins in two species of marine crabs by hemagglutination assay using mammalian erythrocytes. Hemagglutination assay results showed that the hemolymph of the marine crab Grapsus albolineatus showed the highest HA titer with rat erythrocytes. HA titer of the crab Leptodius sanguineus varied from 0 to 32 with all the tested erythrocytes.  Among the various tissues of Grapsus albolineatus analyzed for the presence of agglutinins, hemagglutination activity was observed in the hemolymph and hepatopancreas with rat erythrocytes. HA was determined by both male and female crabs of Grapsus albolineatus. HA activity increased with an increase in animal size. Biochemical factors like water, protein and calcium content of the hemolymph did not have any influence on the HA titer.