Background: The seaweed Halimeda macroloba has been used in the pharmaceutical and nutraceutical industries, but no research has described its invivo activity. Therefore, the current study is done to explore the antidiabetic, hypolipidemic, and antioxidant properties of hydroalcoholic extract of H. macroloba (HME) in Wistar rats. Methods: HME was prepared using 70% alcohol as a solvent using maceration for 72 hours. Nicotinamide (i.p.,110mg/kg) and streptozotocin (i.p.,45mg/kg) were given to induce diabetes and the rats were screened for confirmation of diabetes after 72 hours. Following induction, the rats were randomly divided into seven groups and animals were treated with two doses of HME and conventional medications. Weekly monitoring of body weight and fasting blood glucose with monthly lipid profiles were measured and on the 90 th day, antioxidant parameters and HbA1c were measured. Histopathological analysis was performed on the renal liver and pancreatic tissues. Results: Significant improvements have been seen in body weight, Fasting Blood Glucose and reduction in HbA1c following treatment with HME (100mg/kg and 200mg/kg). Similarly, HME substantially raised HDL levels while lowering LDL, TC, and TG. Comparing the HME groups to the untreated diabetic rats, there was significant raising in the antioxidant levels of GSH, CAT and SOD. However, compared to diabetic rats, HME groups had lower levels of MDA. Comparably, HME reversed the histological alterations and restored the liver, kidney, and pancreas functions. Conclusion: The overall results show administering HME improved BW, HbA1c, and glycemic management. Additionally, the lipid profiles and antioxidant activities have been considerably enhanced.