Studies have suggested that 1-α-OH-vitamin D₃ and green tea polyphenols (GTPs) are promising dietary supplements for mitigating chronic inflammation-induced fibrosis of vessels because of their anti-inflammatory properties. This study evaluated (1) the impact of 1-α-OH-vitamin D₃ on myocardial fibrosis in female rats with chronic inflammation and (2) if 1-α-OH-vitamin D₃ and GTPs have an additive or synergistic effect to attenuate myocardial fibrosis in these female rats. A 3-month study of a 2 (no 1-α-OH-vitamin D₃ vs. 0.05 μg/kg 1-α-OH-vitamin D₃, five times per week) ×2 (no GTPs vs. 0.5% GTPs in drinking water) factorial design in lipopolysaccharide (LPS)-administered female rats was performed. Additionally, a group receiving placebo administration was used to compare with a group receiving LPS administration only to evaluate the effect of LPS. Masson's Trichrome staining evaluated myocardial fibrosis in coronary vessels and surrounding myocardium. Spleen cyclooxygenase-2 mRNA expression was determined by real-time polymerase chain reaction. Total lipid profiles were also determined. Whole blood was used for differential cell counts. Data were analyzed by two-way analysis of variance followed by mean separation procedures. At 3 months LPS administration induced myocardial fibrosis in vessels and surrounding myocardium, spleen cyclooxygenase-2 mRNA expression, and elevated leukocyte counts, whereas both 1-α-OH-vitamin D₃ administration and GTPs supplementation significantly attenuated these pro-inflammatory events. The inhibitory effects of 1-α-OH-vitamin D₃ and GTPs seem to be an individual effect, instead of an additive or synergistic effect. 1-α-OH-vitamin D₃ and GTPs lowered red blood cell counts, hematocrit, and hemoglobin. Neither 1-α-OH-vitamin D₃ nor GTPs affected lipid profiles. In summary, both 1-α-OH-vitamin D₃ administration and GTPs supplementation mitigate myocardial fibrosis through suppression of a chronic inflammation innate immune response.