To investigate the antidiabetic activity of metabolite from novel strain of endophytic fungi isolated from four different mangrove plants namely Avicennia marina, Acanthus ilicifolius, Rhizophora mucronata and Rhizophora apiculata. The crude extracts of three different solvents were extracted and analyzed for a- glucosidase and a-amylase inhibitory assay done with various concentrations (250, 500, 750 and 1000 μg/ml) and were compared with standard drug acarbose. The MTT assay was done on L929 cell lines of the crude extract to predict its cytotoxic effect. The results showed that crude extract of VITNG3 strain had prominent a-glucosidase and a-amylase activity with an inhibition percentage of 73.7±1.25 and 32.17±1.18 in an IC50 range of 367.6 μg/ml and 101.0 μg/ml respectively. Further, the cytotoxic effect on L929 cell lines of the EtOAc crude extract of Collectotrichum siamense starin VITNG3 showed a viability of 74.33% at 1000 μg/ml concentration and thus it was considered as less toxic. A new strain, Collectotrichum siamense starin VITNG3 was isolated from the leaf of Acanthus ilicifolius had satisfactory anti-diabetic activity for type 2 diabetes, which will further be confirmed by in vivo studies. © 2018 World Research Association. All rights reserved.