The nematode Setaria equina usually reside in body cavities and do not cause clinical symptoms. From time to time, however, these parasites can be located in the scrotum and spermatic cord inflicting pain and edema in these body parts. The aim of the study was to describe the case of the nematode Setaria equina found in the vaginal sac of the stallion's scrotum. During the study, thorough examination of 50 isolated testicles of 25 stallions was conducted. The horses were obtained post-slaughter from the local slaughterhouse near Krakow. In one of examined stallions, two females of Setaria equina of 80 and 110 mm in length were found attached to the surface of the testicle. A part of one of the nematode was found in the space between the surface of the testicle and the epididymis. During the examination of the testicle sections, chronic inflammation (orchitis chronica) and focal necrosis perivascularis were found.