Incidental damage to cultural property remains one of the challenges of protecting such property under international humanitarian law (IHL). This issue was evident during the Ramadan War between the United States-Israel and Iran, in which several Iranian cultural properties, including Golestan Palace and Naqsh-e Jahan Square, suffered damage due to the secondary effects of powerful explosions. Employing a descriptive-analytical methodology and drawing on the Ramadan War as a case study, this research addressed this question: How does international law protect cultural property against incidental damage in armed conflicts? The findings indicate that IHL, at the intersection of the principles of distinction, necessity, proportionality, and precaution, establishes an obligation to prohibit excessive incidental damage to cultural property in relation to the anticipated concrete and direct military advantage. This is reflected in Additional Protocol I to the 1949 Geneva Conventions, the 1954 Hague Convention and its Second Protocol, and customary international law. Furthermore, violation of this obligation entails legal accountability from the perspective of the law of international responsibility and international criminal law. The facts of the Ramadan War demonstrate the infliction of excessive incidental damage on Iranian cultural property through the failure to observe the principles of proportionality and precaution. Such damage, while potentially constituting a war crime, also provides, under international responsibility, the possibility of claiming compensation from the offending states and receiving international assistance for reconstruction from relevant institutions.