Genetic determinants of clinical response to Janus kinase inhibitors (JAKi) in rheumatoid arthritis (RA) remain unclear. We performed a genome-wide association study (GWAS) of 6-month disease activity, using DAS28 as a proxy for treatment response, in JAKi-treated Korean RA patients. Ninety-nine patients were recruited from three tertiary hospitals; 85 with complete follow-up were analyzed. JAKi included baricitinib (30.6%), tofacitinib (29.4%), upadacitinib (35.3%), and filgotinib (4.7%). Genotyping was conducted with the Korea Biobank Array (KoreanChip), followed by standard QC, PCA, and Korean reference–based imputation. Post-imputation QC yielded 8,004,664 variants. Associations with 6-month DAS28 were tested by PLINK v1.9 linear regression adjusted for age and sex (suggestive P<5×10⁻⁶). Concomitant steroid use was linked to higher 6-month DAS28 (2.98±0.98 vs 2.37±0.75; P=0.01), whereas JAKi type and methotrexate use were not. In the GWAS, five SNPs reached suggestive significance (P<5×10⁻⁶), including rs141379075, rs6599628, rs1412392, rs1785731, and rs183330260. These findings suggest potential loci related to JAKi response, warranting replication in independent cohorts and further investigation.