Abstract The importance of marine algae as potentially prolific sources of functional ingredients has been well known. It is due to their valuable health beneficial effects and might represent a lead in the development of new pharmaceutical agents. Kappaphycusalvarezii (Rhodophyceae), marine red algae which mainly harvested in east Malaysia and an important resource for production of carrageen an. Diabetes mellitus is a heterogeneous metabolic disorder affecting 2–5% of the adult population in developed countries. Worldwide prevalence figures give an estimate of 130 million people in 2000 and 300 million in 2025, perhaps, it might increase to 552 million by 2030. Edible marine macroalgae are tested around the world for their ability and potential in anti-diabetic effects. Therefore, this study aim to investigate the Antidiabetic effect of K. alvarezii extracts at doses of 100 mg/kg and 200 mg/kg on Streptozotocin-induced type II diabetic ICR mice. Changes in plasma glucose level and body weight in mice treated with extracts before and after treatments were evaluated. Pancreas and blood from mice was obtained separately and followed by different assays in order to investigate the effect of K. alvareziion diabetes-induced mice. Pancrease were grounded into fine powder in liquid nitrogen and used for RNA extraction by R&A-BlueTM Total Extraction Kit. Real-time PCR was taken part to study the gene expression of the Insulin-related gene. Blood serum were separated from the blood and tested for the renal function. After the treatment in a period of 8 weeks, K. alvarezii treated diabetic mice experienced progressive plasma glucose reduction, although it is not significantly. Furthermore, 100 mg/kg and 200 mg/kg K. alvarezii had up regulated the insulin mRNA expression in the late phase of RT-qPCR. Normal renal function was found in the results of blood test. In conclusion,100 mg/kg and 200 mg/kg K. alvareziidid not significantly showed the Antidiabetic effect, however, pancrease is not the only part of the body which playing a role in plasma glucose regulation. The plasma glucose reduction from the diabetic mice probably regulated from the other organ such as renal and liver. Thus, further investigation shall be continued in order to specifically identify the mechanism.