This study looked into the atherogenicity of certain flavonoids in streptozotocin-induced diabetic rats, where a single and a mixed dose of Quercetin (QUE), Curcumin (CUR), and Silymarin (SIL) were administered. Methods: The rats were given a single intraperitoneal (i.p.) injection of 45 mg/kg b.wt. of streptozotocin to develop diabetes. Conventional spectrophotometric methods were used to analyse serum lipid profiles, whereas standard equations were used to compute atherogenicity, atherogenic indices/coefficients, and serum lipid ratios. Results: Serum total cholesterol (TC) concentrations in experimental rat groups ranged from 0.98 ± 0.04 mmol/L to 1.69 ± 0.11 mmol/L (p < 0.05). The concentration of serum high-density lipoprotein (HDL) in untreated diabetic rats was substantially lower (p < 0.05) than in treated diabetic rats. The atherogenic risk indices (ARI) of treated diabetes groups ranged from 3.88 0.79 to 6.83 0.24, while the ARI of the untreated diabetic group was 14.57 ± 0.83. The atherogenic index of plasma (AIP) versus LDL concentrations of the experimental rat groups yielded a reasonably well-fitting regression line (R2 = 0.5723). Flavonoid-treated diabetic groups had atherogenic protection ranging from 53.10 to 73.38%. Conclusion: This study found that CUR, SIL, and a combination of the two with QUE provided diabetic rats with a disproportionately high level of protection against atherogenic consequences.