This study aimed to evaluate the oral supplementation of astaxanthin (ATX) on inflam- matory markers in 3-year-old Arabian racehorses. Despite the recognized antioxidant and anti- inflammatory properties of ATX observed in vitro in rodent models and in human athletes, the effects in equine subjects remain unknown. This study involved a controlled trial with 14 horses receiving either ATX (six horses) or a placebo (eight horses), monitored over four months of race training. Inflammatory cytokines: TNFα, IFNγ, IL-6, IL-10, and prostaglandin E (PGE), were mea- sured monthly to assess the impact of ATX on the inflammatory response. The results indicated no significant differences in measured parameters between the ATX and the control group during the study. However, a significant time-dependent decrease in TNFα and IFNγ levels (p = 0.001) was observed in both groups, suggesting that regular training naturally modulates inflammatory responses. Moreover, positive correlations were noted between TNFα and IFNγ (p < 0.001) in the early phase of the study and between IL-6 and IL-10 (p = 0.008) in the later phase. Hematological parameters remained stable and within reference ranges, indicating no adverse effects of ATX sup- plementation. Performance metrics, including the number of races completed and wins, showed no significant differences between groups, suggesting that ATX did not enhance athletic performance under the study conditions. Overall, while ATX supplementation affected neither cytokine levels nor performance in Arabian racehorses, the natural anti-inflammatory effects of regular training were evident. Further research is needed to explore potential benefits of ATX supplementation under different conditions, such as in horses with subclinical inflammation or varying training regimens, to fully clarify its role and applications in equine sports medicine.