Streptozotocin is a naturally occurring nitrosourea, widely used to induce insulin-dependent diabetes mellitus in experimental animals because of its toxic effects on islet beta cells. This study was untertaken to investigate the effect of methanolic extract of barks of Kandelia Rheedii W. & A. (KRM) and aqueous extract of Kandelia Rheedii W. & A. Barks (KRA) against streptozotocin induced diabetes. Hyperglycaemia was induced by administering a single dose of streptozotocin (50 mg/kg b.w) following evaluation of antidiabetic activity of extracts of kandelia rheedii and its traditional formulation. Biochemical parameters were determined and pancreatic tissues from various groups were processed for histological examination. Significant (p < 0.05) reduction in glucose and lipids was observed. Significant difference in biochemical parameters was observed when compared to control group. Histopathological data showed improvement in hepatocyte and pancreatic β-cells islets architecture. Further studies to standardise the extract and evaluation of safety profile in long-term toxicity studies are recommended for safe and effective antidiabetic nutraceuticals development.