The majority of natural diabetic medications come from fruits and vegetables. These natural medications help protect humans from negative impacts of chemical antidiabetics by scavenging free radicals. The present study aimed to explore the antioxidant and antidiabetic properties of methanolic extract of fruits of Hibiscus sabdariffa Linn. (MEHSF) in alloxan-induced Swiss albino diabetic mice. The dried coarse powder of Hibiscus sabdariffa Linn. fruits was subjected to methanol extraction. The antidiabetic activity was determined by using alloxan-induced (80 mg/kg body weight) diabetic mice. Following a 15-day treatment period, serum biochemical parameters including total cholesterol (TC), triglyceride (TAG), LDL-cholesterol (LDL), HDL-cholesterol (HDL), serum glutamic pyruvic transaminase (SGPT), and serum glutamic-oxaloacetic transaminase (SGOT) enzymes were estimated. The antioxidant activity was evaluated through a DPPH and ABTS free radical scavenging assay. Total phenolic content and total flavonoid content were assessed using established methods. MESHF, containing polyphenolic and flavonoid compounds, exhibited antioxidant properties. A 100 and 200 mg/kg significantly (p < 0.05) lowered the blood glucose levels and improved biochemical parameters such as TC, TAG, LDL, and HDL in diabetic mice. Further, MESHF significantly (p < 0.05) reduced the activity of the SGPT and SGOT in diabetic mice compared to untreated diabetic mice. These results suggest that MEHSF with promising antioxidant and antidiabetic potentials can be considered to be a probable new resource of the antidiabetic agent.