The agar gel diffusion test (AGDT) was applied to detect Fasciola infection in several regions of Vietnam where equipment for fecal examination such as a microscope is not readily available. A 1% solution of agar dissolved in 10% saline, and the antigen prepared from adult individuals of Fasciola sp. were used for the test. The test was specific for Fasciola infection, which was detected in the sera from about 50% of the cattle and water buffaloes examined. The gel and antigen can be stored in a refrigerator for more than 3 months and used for the test. The results of this study revealed that the agar gel diffusion test could become a useful tool to diagnose fasciolosis in cattle and buffaloes at the Regional Animal Health Centers in Vietnam.