Diabetes causes elevated blood sugar levels, and it has been categorized as one of the most frequent causes of death worldwide. This work aimed to analyze and compare the nutraceutical and therapeutic efficacy of fenugreek seeds (FSs) (Trigonella foenum-graecum) and black cumin seeds (BCSs) (Nigella sativa) against streptozotocin-induced diabetes mellitus in albino rats. FS and BCSs were evaluated for proximate analysis, phytochemicals, and antioxidant activities. Male albino rats were used to evaluate the in vivo antidiabetic activities of these medicinal plants for 42 days. Blood samples were drawn at regular intervals of 1 week to analyze blood glucose, plasma insulin, and cholesterol levels and to determine the homeostatic model assessment of insulin resistance (HOMA IR) index. At the end of the trial, pancreas tissue was also collected for histological examination. Results of the proximate analysis showed the significant presence of moisture, ash, fat, protein, and fiber. Antioxidant parameters like 2,2-diphenyl-1-picrylhydrazyl, total phenolic content, and total flavonoid content were found to be significant. There was a significant (p < 0.05) decrease in blood glucose level, serum cholesterol level, and insulin resistance in treatment groups T3-T5. Insulin and body weight results of treatment groups were significant (p < 0.05) compared to streptozotocin-intoxicated animals. Histological examination revealed the nutraceutical impact of selected herbal plants due to enhancing impact on the size and the number of β-cells in the pancreas. Findings of current research work explore the antidiabetic capacity of selected nutraceutical and medicinal plants.© 2024 Institute of Food Technologists.