WHIRLY proteins, known for their DNA/RNA-binding capabilities conferred by a highly conserved WHIRLY domain, are integral to plant defense mechanisms. However, the role of OsWHY1 in rice immunity remains to be clarified. We examined OsWHY1 expression after treatment with exogenous hormones, PAMPs, and Magnaporthe oryzae. We generated OsWHY1-overexpressing rice plants and performed yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC), transcriptome, and RT-qPCR analyses. OsWHY1 expression was upregulated by exogenous hormones and PAMPs, with a significant increase at 24 h post-inoculation with M. oryzae. Overexpression of OsWHY1 correlated with reduced resistance to M. oryzae. Y2H and BiFC assays demonstrated that OsWHY1 could form homomeric complexes within the chloroplast, and OsWHY1 did not possess transcriptional activation activity. Transcriptome profiling of OsWHY1-overexpressing plants revealed significant downregulation of genes associated with glutathione transferase activity. Chitin-induced reactive oxygen species (ROS) accumulation was diminished in OsWHY1-overexpressing plants compared with the Nipponbare (NPB) control. The transcriptional levels of key stress- and defense-related genes, including OsWAK1, OsWRKY53, OsPR2, OsSAG12, OsHSP58.7, OsCATB and OsMYB1R, were markedly downregulated in OsWHY1-overexpressing plants. Collectively, these findings indicate that OsWHY1 functions as a negative regulator of rice immunity against M. oryzae by suppressing the expression of defense-related genes. Thus, our study identifies OsWHY1 as a negative immune regulator and suggests that its manipulation could be a strategy for breeding blast-resistant rice varieties.