Two novel multiplex polymerase chain reaction (mPCR) assays were originally developed for detecting nine targeted virulence-associated genes of five categorized diarrheagenic Escherichia coli (DEC). The mPCR assay 1 included five primer sets (stx1, eaeA, invE, STp gene, and astA), and assay 2 included four primer sets (stx2, aggR, STh gene, and LT gene). The two mPCRs showed 100% specificity in identifying the reference strains without nonspecific bands, and 51 DEC and 38 astA gene-positive E. coli strains from 683 E. coli-like isolates. Our mPCR methods showed high sensitivity and specificity for detecting nine virulence genes of DEC strains. We proved that these methods will contribute to reducing the cost for the reagents of mPCR reported elsewhere and could, therefore, contribute to the diagnosis of DEC in clinical laboratories.