Background: Aegle marmelos (L.) Correa is a widely found plant in India as well as in South Asia. For more than several centuries, it is being widely used for its medicinal properties. Objective: The objective of this study was to evaluate the biochemical changes in alloxan‑induced diabetic rats treated with methanolic leaf extracts of A. marmelos. Materials and Methods: Six treatment groups, namely control, diseased, standard (glimepiride), low dose (100 mg/kg), medium dose (250 mg/kg), and high dose (500 mg/kg) of methanolic leaf extracts, were used in the study. The biochemical effects were evaluated by the determination of bodyweight, blood glucose, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), total proteins, serum albumin, serum creatinine, and alkaline phosphatase. Results: A significant increase in the bodyweight of the animals was observed in the high‑dose treated animals (350.0 ± 6.15) when compared to the diseased group animals (241.0 ± 7.23). A significant decrease in the blood glucose, SGOT, and SGPT levels was observed in the high‑dose treated animals (142.3 ± 20.52, 71.6 ± 4.8, and 24.5 ± 2.42) when compared to the diseased group animals (292.8 ± 29.34, 146.3 ± 11.12, and 74.5 ± 2.88), respectively. Similarly, total proteins, serum albumin, serum creatinine, and alkaline phosphatase levels of the high‑dose treated animals were also significantly decreased (6.1 ± 0.26, 4.2 ± 0.22, 0.4 ± 0.18, and 109.2 ± 14.58) when compared to the diseased group animals (9.7 ± 0.27, 5.4 ± 0.26, 1.0 ± 0.22, and 257.2 ± 8.22), respectively. Conclusion: Through the biochemical changes, it is evident that the high dose of methanolic leaf extract of A. marmelos can be used in the treatment of diabetes and its complications.