Lectins are carbohydrate-binding proteins of nonimmune origin from microorganisms, animals or plants. They are multivalent molecules, possessing sugar-binding sites to agglutinate cells and precipitate polysaccharides, glycoproteins, peptidoglycans, and glycolipids. Sebastiana jacobinensis ("pau de leite") belongs to the Euphorbiaceae family and is used as a medicinal plant with anti-inflammatory, healing and anticoagulant activities. The aim of this work was to purify and partially characterize S. jacobinensis bark lectin (SejaBL). The lectin was obtained through precipitation with ammonium sulphate followed by ion exchange chromatography in CM-Cellulose. Pure lectin was evaluated in relation to thermal stability, pH values, inhibition with carbohydrates and glycoproteins, ion influence, resistance to oxidizer agents (malonaldehyde, urea, SDS, and EDTA) and polyacrylamide gel electrophoresis. SejaBL agglutinated different erythrocytes (humans, A, AB and O, as well as rabbit, mouse, rat and chicken). None used monosaccharides inhibited SejaBL HA while glycoproteins (casein, fetuin, asialofetuin, ovalbumine, thyroglobulin and bovine serum) totally abolished activity. SejaBL was active after heating until 70 °C for 30 min; no activity was detected after 100 °C by 1 h. Ions or different pH values (2.5 to 10.5) did not alter lectin HA. Also, SejaBL activity diminished after treatment with SDS, EDTA, urea or malonaldehyde. The lectin revealed one band (glycoprotein) by electrophoresis to native and acid protein or by SDS-PAGE with an apparent molecular mass of 50 kDa. In conclusion, the purification protocol used was efficient to obtain a lectin with stable activity under high temperatures, different pH values and oxidizer agents.