Mycotoxins are toxic secondary metabolites of fungi, which can be found in cereal grains and animal feeds. The occurrence of mycotoxins in feed of livestock animals is well investigated. In contrast, only limited information is available on the occurrence of mycotoxins in horse feed as well as on their effects on horse health. The aim of this study investigate the occurrence of the mycotoxins aflatoxins (Afla), fumonisins (FUM), zearalenone (ZEN), ochratoxin A (OTA), deoxynivalenol (DON) and ergot alkaloids in horse feed in Europe. Hay, straw and concentrate feed samples (n = 135) were collected from different countries of Europe in 2014. Samples were analyzed by liquid chromatography – tandem mass spectrometry (Streit et al., 2013). In total, mycotoxins could be found in 83% of all tested samples. Ergot alkaloids (e.g., ergotamine, festuclavine) were detected in 63% of the samples and therefore represented the most frequently occurring mycotoxin in our survey. In the individual samples, concentrations up to 1,230 µg/kg were determined. In addition, a high prevalence of DON (60%) and ZEN (54%) was observed. Maximum concentrations of 3,800 µg/kg and 200 µg/kg were measured for DON and ZEN, respectively. FUM was detected in 16% of the feed samples, maximum concentration measured was 330 µg/kg. In contrast, Afla (1.5%) and OTA (3%) were detectable in only a few of the feed samples. Results of this study clearly show that mycotoxins are frequent contaminants of horse feed, although usually only high quality feed is given to horses. There are only scattered reports on the effects of mycotoxins on horses. However, it is known that horses are extremely sensitive to FUM (Caloni et al., 2011) and also negative effects of ZEN have been reported (Minervini et al., 2006). Furthermore, ergot alkaloids are described to induce dystocia, agalactia and lameness in horses (Cross et al., 1995; Douthit et al., 2012). Therefore, an effective mycotoxin risk management program can help to protect horses against negative effects of mycotoxins.