Increased life expectancy is a trend observed not only in humans but also in horses. In people, aging is often associated with cognitive deterioration, such as Alzheimer’s disease, which shares similarities with age-related cognitive decline in dogs. However, the aging process in horses remains largely unexplored. This study aims to investigate the presence of blood biomarkers linked to cognitive degeneration in horses. A total of 23 Arabian horses were examined, and serum levels of β-amyloid peptides (Aβ40 and Aβ42) and phosphorylated tau protein (pTau181) were measured, molecules recognized as reliable indicators of cognitive decline in other species. Notably, Aβ42 was undetectable in all samples. While no correlation was found between age and either Aβ40 or pTau181 levels, a significant positive correlation emerged between Aβ40 and pTau181 concentrations. Interestingly, none of the horses showed behavioral changes or clinical signs suggestive of cognitive dysfunction. This absence of symptoms may be attributed to the undetectable levels of Aβ42, the isoform considered key in triggering cognitive degeneration through tau phosphorylation, even if potentially present at higher levels than those typically found in healthy humans.