Twenty species of marine invertebrates from the Brazilian coast were screened for hemagglutinating/hemolytic activity. In at least twelve tested species, hemagglutinating activity was different for different blood types, suggesting the presence of lectins. Extracts from four species showed hemolytic activity. Two new lectins were purified from the marine sponge Cliona varians (CvL-2) and sea cucumber Holothuria grisea (HGL). CvL-2 was able to agglutinate rabbit erythrocytes and was inhibited by galactosides. The hemagglutinating activity was optimal in pH neutral and temperatures below 70 °C. CvL-2 is a trimeric protein with subunits of 175 kDa. On the other hand, HGL showed both hemagglutinating and hemolytic activity in human and rabbit erythrocytes, but hemolysis could be inhibited by osmotic protection, and agglutination was inhibited by mucin. HGL was stable in pH values ranging from 4 to 10 and temperatures up to 90 °C. In electrophoresis and gel filtration, HGL was a monomeric protein with 15 kDa. CvL-2 and HGL showed different levels of toxicity to Artemia naplii. CvL-2 showed LC50 of 850.1 μg/mL, whereas HGL showed LC50 of 9.5 µg/mL.