Tritrichomonas foetus is a parasitic protozoan that causes large-bowel disorders in domestic cats worldwide. Between 2020 and 2024, 1606 feline stool samples were tested for T. foetus. The aim of this study was to determine the prevalence of T. foetus infection among cats with diarrhea reported within the last 6 months, and to assess age and sex as risk factors for T. foetus infection. The diagnostic method of choice was nested PCR with modifications to reduce potential reaction inhibition. Overall, T. foetus DNA was detected in 10.6% (170/1606) of cats, with the highest prevalence observed in animals younger than one year, 14.9% (106/711). This study confirms that T. foetus infection is common in domestic cats in Poland. Therefore, this parasite should be included in the differential diagnosis protocol for feline patients with large-bowel diarrhea.