Ochratoxin A (OTA) is a renal mycotoxin and transplacental genotoxic carcinogen. The aim of this study was to evaluate the natural occurrence of OTA in equine blood samples and its placental transfer. For the assessment of OTA levels, serum samples were collected from 12 stallions, 7 cycling mares and 17 pregnant mares. OTA was found in 83% of serum samples (median value = 121.4 pg/mL). For the assessment of placental transfer, serum samples were collected from the 17 mares after delivery and from the umbilical cords of their foals, after foaling. Fourteen serum samples from pregnant mares contained OTA (median value = 106.5 pg/mL), but only 50% of their foals were exposed (median values = 96.6 pg/mL). HPLC analysis carried out on four serum samples (collected from two mares and their respective foals) supported the ELISA results on OTA placental transfer. This is the first report on the natural occurrence of OTA in horse serum samples and placental transfer in horses.