The worldwide contamination of poultry feeds with aflatoxins and ochratoxin A (OTA) independently and in co-occurrence has been reported in several countries. However, there is paucity of information on the co-occurrence of aflatoxins and OTA and their detection by immunoassay in Nigerian poultry feed. Fourty-seven locally formulated poultry samples collected from 13 locations within Southwestern Nigeria were analyzed for total aflatoxins (TA) and ochratoxin A (OTA) using the Immunoassay method. The potential toxicities of the samples were tested by the Clarias gariepinus day-old larvae bioassay. Approximately 98.2% samples were positive for TA and OTA with concentrations above the limits of quantitation. The ranges of TA and OTA in the samples were <4>C. gariepinus larvae was concentration dependent and 17, 21 and 7 samples containing the co-occurring toxins showed high, moderate and low toxicities respectively. On the average, 88.9% and 65.5% of the total samples had concentrations above the EU permissible limits for TA in immature and mature poultry feed respectively. The overall contamination risk for TA and OTA in samples in a significant (P = 0.01) decreasing order was: chick mash, broiler finisher, layers mash, broiler starter and growers mash.