We have developed a reverse transcription (RT)-multiplex PCR assay with fluorescent dye-labeled primers for detection of 12 pathogens, including 9 bacteria and 3 viruses, that are highly associated with food-borne gastroenteritis outbreaks. This assay has a great advantage of comprehensive detection of bacterial DNAs and viral RNAs. PCR products of pathogens are easily discriminated by fluorescent color and fragment size visualized under ultraviolet light without staining, after electrophoresis. Simultaneous extraction of bacterial DNAs and viral RNAs were achieved using a commercial viral RNA extraction kit with some modification. After RT reaction, multiplex PCR was carried out with 3 primer sets (A, B, and C) labeled with 3 to 4 different colors of fluorescent dyes. Primer set A was designed for diarrheagenic Escherichia coli. Primer set B was for Salmonella spp., Campylobacter jejuni and C. coli, and Vibrio parahaemolyticus. Primer set C was for Clostridium perfringens, Norovirus, Sapovirus, and Astrovirus. Upon analysis of 45 food-borne gastroenteritis outbreaks and 15 sporadic cases, this assay had nearly corresponding sensitivity and specificity compared with conventional methods, such as bacterial cultivation and monoplex PCR. This assay can be completed within 6 to 7 hours and is considered effective for rapid screening of food-borne bacteria and viruses.