Herbal remedies are considered convenient for the management of diabetes due to their traditional acceptability, availability, and less side effects than oral hypoglycaemic agents. Tree fern, Cyathea nilgiriensis (CYATHEACEAE) is popular among the traditional healers of Kolli hill, Namakkal because of its medicinal value. The present research attempts to assess the antidiabetic and antihyperlipidemic effects of ethanolic extract of Cyathea nilgiriensis pith powder on STZ induced diabetic model. STZ induced albino rats were treated with (200 mg/kg of b.wt. dose) ethanol extract of C. nilgiriensis pith powder for 48 days. The treatment restored the elevated levels of body weight, blood glucose, and HbA₁C. Further, it significantly increased serum insulin level of STZ induced diabetic rats. Total cholesterol, triglycerides, LDL, and very low density lipoprotein (VLDL) were elevated and high density lipoproteins (HDL) level was decreased in diabetic rats. The elevation was markedly controlled near to normal level in extracts treated diabetic rats. Decreased HDL level was significantly increased by treatment with ethanol extract of C. nilgiriensis. From the above experimental responses, it is concluded that 234the C. nilgiriensis proved that it is one of the best promising and emerging drug against diabetes mellitus and its complications.