Sogatella furcifera and Laodelphax striatellus are serious pests of rice plants that have developed fipronil resistance in Asia. The A2′N mutation in the RDL γ-aminobutyric acid (GABA) receptors conferred fipronil resistance and was suggested to be a heterozygous mutation. We have developed a rapid PCR-RFLP assay to detect the A2′N mutation in individual insects. This assay is useful for monitoring S. furcifera and L. striatellus carrying the A2′N mutation in field populations and may contribute to managing these pests.