Various plant actives have been reported for their therapeutic potential in obesity so far and plant polysaccharides are one of them. Naturally occurring non-starch polysaccharides are widely known for their anti-oxidant, immunomodulatory, anti-diabetic and anticancer activities as well in various in vitro and in vivo test systems. This paper focuses on one such crude polysaccharide fraction isolated from the leaves of the plant Vitex negundo which was tested for its anti-obesity activity in male db/db mice at 50 mg/Kg dose via both subcutaneous and per oral route of administration for 7 days. The activity via both the routes was compared with pair-fed and normal control animals for various parameters such as daily food intake, body weight, fasting serum glucose, insulin and triglyceride levels as well as changes in glucose levels during oral glucose tolerance test (OGTT). Obtained results demonstrate a significant reduction in food intake, body weight and fasting glucose levels in crude polysaccharide treated animals which are suggestive of its anti-obese activity. Further, a remarkable increase in fasting insulin and a significant decrease in glucose intolerance in crude polysaccharide treated animals was also observed, which indicate its anti-diabetic activity. Thus, this study primarily establishes a positive role of the crude polysaccharide from V. negundo leaves in treatment of both obesity and type 2 diabetes mellitus.