Viscum album and its endophytic fungal species lectin are reported as antioxidant, antimicrobial, anti-inflammatory and anticancer activity. The present investigation was undertaken to in vitro (by enzymes inhibition) and in vivo antidiabetic activity of endopytic fungi, Alternaria species N-acetyl-galactosamine, 54 kDa protein lectin in alloxan induced diabetes in rats. Endophytic fungal lectinwas orally administered at 400 mg/kg body weight (BW) dose to alloxanized mice (blood glucose>200 mg/dl). Various diabetic parameters were studied and compared with untreated mice. Furthermore, Matrix Assisted Laser desorption Ionization Time Of Flight Mass Spectroscopy (MALDI-TOF-MS) was employed to reveal the characteristics and identification of peptides.The lectin was confirmed by hemagglutination, PAS staining and it is N-acetyl-galactosamine, 64 kDa glycoprotein. The endophytic fungal lectin inhibited the three important diabetic enzymes viz., α-amylase (85.26 ± 1.25), α-glucosidase (93.41 ± 1.27) and sucrase (81.61 ± 1.05) strongly. The N-acetyl-galactosaminelectin treated diabetic rats showed significantly increased the body weight (8.50%) compared with the standard drug (9.01%) after 14 days of treatment. The lectin treated rats shown regeneration of pancreatic tissues, ducts and walls, acini, blood vessels, blood capillaries, islet capsules and cells and all these were in accordance with format only and recovery has been observed. The lectin treated diabetic rats also reduced the levels of urea (43.7 ± 5.8), creatinine (0.32 ± 0.01), serum cholesterol (103.54 ± 2.13), triglycerides (124.68 ± 2.49), aspertate aminotransferase (138) and alanine aminotransferase (57) and this results confirms the health of the animal when compared to standard drug. The study provides that endophytic fungal lectin could exert a protective effect against β-cell damage by its anti-inflammatory effects and aids regeneration might through stimulation of ductal stem cells. However, further experimental studies are still needed for more details on lectin as an adjuvant in the management of diabetes mellitus. The present results revealed that, endophytic fungal lectin possess potent anti-diabetic activity and regenerated the cells or tissues in diabetic rats.