In this retrospective study, the tolerance to subcutaneus mistletoe injections (Viscum album L.), adverse reactions and possible indications have been evaluated in feline patients of a small animal clinic. Among the 22 cats treated between 2008 and 2013, 4 did not accept the injections done by the owner, 7 showed slight short time adverse reactions, that disappeared spontaneously. No long term (more than 70 days) adverse reaction directly related to the Viscum album treatment could be identified. This study shows that Iscador(®) can be injected subcutaneously without a risk of worsening of the clinical signs or exacerbation of tumors. The antitumoral, but also immune-modulating and anti-inflammatory properties offer interesting treatment opportunities for dermatologic, odonto-stomatologic or allergic patients.