MSc.DissertationAflatoxins (AF) and fumonisins (FM) are major foodborne mycotoxins of public health concerns that infect maize and groundnuts which are the main components of cereal based complementary foods with formula (CBCF-F). The study was conducted to: determine and compare the quantity of total AF and FM among different types of CBCF-F, identify the factors that might influence high contamination of AF and FM in CBCF-F, and assess awareness and perceptions of the processors about AF and FM contamination in cereals. The study design was cross-sectional, involving 60 processors whose 70 CBCF-F were collected for laboratory analysis. High Performance Liquid Chromatography and Enzyme Linked Immunosorbent Assay methods were used to quantify total AF and FM in the 70 CBCF-F samples. Data analysis was done using SPSS, and comparisons of the total AF and FM among samples were done with Duncan’s LSD. The results showed that 93 and 98% of CBCF-F samples were contaminated with AF and FM respectively; 32.9% of the samples exceeded the regulatory limit of 10 ppb set by TBS. There was no sample that exceeded the regulatory limit of 2 ppm for total fumonisin. The factors that increased AF contamination in CBCF-F were the use of groundnuts (p < 0.05) and living in rental houses (p < 0.05). Eighty-two (82%) and 95% of the respondents were not aware of AF and FM respectively; 90 had seen molds but 76.7% of them did not associate them with health implications while 28.3 and 48.3% perceived molds as crop diseases and decayed foods with no health implications to human being respectively. It is concluded that infants depending on CBCF-F are exposed to AF and FM contamination. Also, groundnuts and rental houses contribute significantly to increasing total AF in CBCF-F, and the majority of processors of CBCF-F are not aware of multiple occurrences of mycotoxins in cereal products. It is recommended that mycotoxins contamination should be viewed as a cross cutting issue and given priority in Tanzania.