The aim of this study was to determine the effects of seasonal variations on the occurrence of total aflatoxin (AFTotal), aflatoxin B1 (AFB1), ochratoxin A (OTA), and total fumonisin (Ftotal) in the commercially mixed ruminant feed obtained from feed mills located in Ankara, Kırıkkale, Çankırı, Çorum, and Kırşehir provinces using the enzyme-linked immunoassay (ELISA) method. To represent the annual production, 22 samples were collected every quarter over 1 year (a total of 88 samples) starting in September 2012. AFTotal and AFB1 were detected in 72 samples (81.81%), OTA in 84 samples (95.45%), and Ftotal in 83 samples (94.31%). When seasonal changes were taken into consideration, the highest levels of AFTotal, AFB1, and Ftotal (13.57 ± 8.78 ppb, 8.54 ± 6.02 ppb, and 0.70 ± 0.88 ppm, respectively) were found in the summer, while the highest OTA level (57.69 ± 14.59 ppb) was observed in the spring. The results of high-performance liquid chromatography methods confirmed the results of the ELISA method. Consequently, although most of the feed samples were contaminated with mycotoxins, all the amounts were within the limits allowed for feedstuffs in Turkey.