The study was conducted with the objective of reducing aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1), and G2 (AFG2) as a function of extruder operating conditions such as initial moisture content of samples (17% and 21%) barrel temperature (140, 160, and 180 0C), and screw speed (150,200 and 250 rpm) when naturally contaminated composite of corn and fully defatted peanut meal (70/30 ratio) was extrusion-cooked to produce corn flakes. Factorial design was used to conduct the experiment. The amounts of aflatoxin in extruded and unextruded composite samples were measured by using high-performance liquid chromatography (HPLC). Accordingly, the effect of the operating conditions on the physicochemical properties (bulk density, expansion ratio, specific length, fresh product moisture content, water absorption index (WAI), water solubility index (WSI), water holding capacity (WHC), and sensory characteristics (hardness and crispness) on composite of corn and fully defatted peanut meal (70/30 ratio) was investigated. The collected data were subjected to analysis of variance using SPSS statistical soft ware. Extrusion-cooking was observed to reduce aflatoxin (AF) content, which ranged from 60% to 93% depending on the type of AF significantly (P