Granulosa cell tumours are the most common neoplasm of the bovine ovary and present with a wide range of clinical signs. This case series comprises five case reports of ovarian granulosa cell tumours in cattle. The affected animals had different breeds (Red Holstein, Eringer, Swiss Braunvieh, crossbred beef) and ranged in age from 1 year 4 months to 20 years 11 months. The diversity of the cases gives an overview of the diagnostic possibilities as well as the possible treatments and outcomes of the disease. Anti-mullerian hormone (AMH) was measured in one of the affected animals, and was extremely elevated (>150 pmoL/L) compared to reported normal values (<3 pmoL/L). Three animals underwent standing laparotomy with unilateral ovariectomy, and the remaining two animals were slaughtered. One of the cases confirms the previously published reports that malignancy or metastasis is possible in cattle. Another case indicates that successful surgical treatment with subsequent resumption of reproduction is possible. In summary, the initial tentative diagnosis of GCT is made by ultrasound-assisted rectal examination of the genital tract or ovaries and can subsequently be supported by evaluation of AMH levels. The decision to proceed with treatment should be made without delay, as surgical removal of the altered ovary with subsequent resumption of reproductive activity and cessation of undesirable behaviour is possible
