The objective of the study was to determine the causes and the severity of anaemia in pet rabbits (Oryctolagus cuniculus), to classify anaemia and to compare the reticulocyte counts from healthy and anaemic rabbits. Over a time period of 11 years (2000–2011) a retrospective and prospective study of 223 pet rabbits was performed. Based on the clinic’s own reference range for healthy pet rabbits (packed cell volume [PCV] levels 0.33–0.45 l/l), animals with a PCV level below 0.33 l/l were considered anaemic. Anaemia was mostly caused by inflammation (65/223, 29 per cent) and bleeding (54/223, 24 per cent). Seven per cent (15/223) of the rabbits suffered from renal diseases and one rabbit got diagnosed with haemolysis caused by liver lobe torsion. In 14 per cent (32/223) of the rabbits more than one underlying pathomechanism, like inflammation and bleeding, was diagnosed as possible cause of anaemia. In 25 per cent (56/223) of the anaemic rabbits no cause was found. Most anaemias were mild (156/223, 70 per cent). Moderate (43/223, 19 per cent) or severe (24/223, 11 per cent) anaemia was diagnosed more rarely. Anaemic rabbits showed similar reticulocyte counts to healthy rabbits with no significant difference. Therefore, a differentiation of regenerative and non-regenerative anaemia was not possible.