Ovariectomy and ovariohysterectomy are most commonly performed surgical procedures in veterinary medicine. Although they serve as a therapeutical method of various pathological conditions which affect reproductive system, in most cases their purpose is elective castration to prevent unwanted litter. Due to routine performance, significant postoperative complications are rare with these procedures. Ovarian remnant syndrome is an iatrogenic caused condition which occurs in relatively high percentages as a complication after ovariohysterectomy. Main reason for this occurance is inability to remove the whole ovary so remaining ovarian tissue revascularizes over time and retrieves its full function. Active tissue produces estrogen and causes same symptoms of heat as in an intact female – vulvar swelling, sanguinosus vaginal discharge and typical active or passive behaviour. In most cases remnant is found near right ovarian pedicle because the position is hard to reach during surgery. Diagnosis is based on thorough anamnesis and vaginal cytology. Measuring circulating levels of ovarian streoids, provocative GnRH or HCG testing and concentration of Anti-Müllerian hormone are used as an additional confirmation. Most reliable way of successfully diagnosing this syndrome is a diagnostic laparotomy but due to the progress of minimal invasive surgical techniques, its usage is nowdays significantly reduced. Hormone treatment is limited and not recommended long term. Treatment of choice is surgical excision of the remaining mass which can be difficult because the tissue is often inapproachable. Considering high rate of malignant changes accompanying this condition, excised tissue is always sent to patohystological examination in order to prevent and diagnose possible life-threatening neoplasias in timely manner