The Russia-Ukraine war has challenged our understanding of corporate social responsibility (CSR). Whereas CSR is traditionally associated with business self-regulation that benefits business and society, the current conflict has revealed new forms of what we call “partisan CSR.” Based on comprehensive data from Fortune Global 500 corporations, this study discovers that in particular Western corporations have engaged in partisan CSR activities, ranging from (1) strengthening Ukraine’s economy, to (2) enhancing security and protection for Ukrainian citizens, (3) providing military support, (4) weakening Russia’s economy, and (5) supporting the Ukraine in symbolic ways. By comparison, some companies choose to be “neutral”, while exploiting economic opportunities arising from the conflict. This study also discusses major drivers of these CSR responses, including political climate, resource availability and economic dependency, isomorphism, and regulatory requirements. Our findings suggest a shift from political CSR to partisan CSR, which we expect to become more important with growing geopolitical divides and territorial conflicts.