Abstract: Post-weaning diarrhea or edema in piglets caused by F18+ Escherichia coli (E. coli) is a disease which is spreading worldwide; however, due to the lack of a quick and convenient Assay Method, very little data is available about its epidemiology. In this study, a FedF-based indirect Enzyme-linked Immunosorbent Assay (ELISA) was developed which employed a fragment of the FedF protein of F18+ E. coli expressed through genetic engineering. The optimal concentration for the purified protein was found to be 2.25 μg mL-1 with an optimal serum dilution of 1:40. The positive cut-off was established to be 0.381. This FedF ELISA showed high specificity toward F18+ E. coli positive sera and no cross reactivity with positive sera against a variety of other swine pathogens, especially several other E. coli pathogens and other major diarrhea causing pathogens. This FedF-ELISA and an extracted F18 fimbriae antigen based Dot-blot assay were used to assay 146 sera. The two methods showed a total agreement ratio of 93.0%. Seroconversion of experimental infected pigs showed that the sensitivities of the FedF-ELISA and of the Dot-blot assay were approximately equal. The FedF-based ELISA was found to have both specificity and sensitivity for detection of porcine antibodies.