Prolapsus of the urethral mucosa is a very rare condition that occurs in male especially castrated dogs. A 7-year old male, neutered Yorkshire terrier was referred to Clinic of Internal Medicine, Veterinary Faculty of Istanbul University, constituted the material of this study. As being informed by the patient's owner lethargy, stranguria and bleeding from the prepuce lasted for the duration of 5 days and castrated 3 years ago, was also mentioned. Physical examination at the time of referral revealed discomfort at the penis region and oversensitivity at the urinary bladder. The urethral mucosa was seen as prolapsed and the mucosa's colour was bright red to dark purple. During the urethral catheterization it was easily passed through the center of the tissue. Severe thrombocytopenia (56x103 µL) and prolonged PT (11 sn) and APTT (21 sn) were detected in haematologic analysis. BUN and creatinine levels were seen in normal ranges. In the urinalysis, pyuria and crystalluria were detected. After the antibacterial and supportive therapies prolonged for 10 days, bleeding from the prepuce disappeared. The patient's problems had finished one month later after the treatment and the prolapsed mucosa healed.