The Brown Plant Hopper (BPH) is a destructive insect pest that is exclusively a monophagous pest on rice plants in rice-growing regions worldwide. BPH populations have evolved into new biotypes, becoming highly destructive to rice crop production. To enhance host plant resistance against the virulent BPH biotypes, this study aimed to introduce major broad-spectrum resistant genes, namely Bph20 and Bph21, derived from IR71033-121-15B (derived from Oryza minuta), into the susceptible elite rice cultivar CO 51. Backcross Inbred Lines (BILs) at the BC2F3 stage, harbouring Bph20 and Bph21, were developed through crosses between CO 51/IR71033-121-15B. A total of twenty BILs, along with the parents and control lines, were screened using the Modified Bulk Seedling Test (MBST) in a replicated trial. The recurrent parent CO 51 displayed an average susceptibility score of 7.5 against the BPH biotype, whereas the BILs exhibited improved resistance compared to the recurrent parent. Among them, BIL #12-2-2-2, BIL #12-2-2-9, BIL #12-2-6-3, BIL #12-2-6-5, BIL #12-2-6-6 and BIL #12-2-6-7 consistently demonstrated resistant reactions with an average score of less than 5 against the BPH biotype. The yield per plant improved from 0.48% to 7.84% in BILs over the recurrent parent CO 51. BIL #12-2-6-6 was recorded as a 7.84% higher yield over recurrent parent CO 51 followed by BIL #12-2-6-3 (7.30%) and BIL #12-2-6-5 (6.53%). This study successfully stacked or introgressed the major broad-spectrum genes Bph20 and Bph21, resulting in highly resistant BILs against the BPH biotype.