In foals, diarrhea is a significant health concern that can be attributed to various nutritional, management, infectious, and other factors. This study was conducted to investigate a case of diarrhea caused by Proteus bacteria in a foal. The foal with diarrhea was recorded according to its age, sex, and breed, and the sample was transferred to the microbiology laboratory on ice. The samples were then cultured in McConkie medium under both aerobic and anaerobic conditions at 37°C. Following the appearance of bacterial colonies, identification was performed using biochemical tests and polymerase chain reaction targeting the 16S rRNA gene. To definitively confirm the isolated bacteria, the reaction product was sequenced, revealing that the isolated bacteria was the causative agent of Proteus diarrhea. The accession number of the identified Proteus bacteria in GenBank is OQ455941. In light of these findings, it can be concluded that Proteus may be a contributing factor to foal diarrhea, underscoring its potential public health significance.