Abstract: Iron plays a pivotal role in the co-evolution of plants and pathogenic microorganisms: it is not only an essential nutrient for both plants and pathogens, but also a crucial weapon in the processes of infection and defense. This article elaborates on the mechanisms by which plants and pathogenic microorganisms acquire iron and regulate their internal iron homeostasis. It introduces two iron-signaling immune pathways in plants: one employs an iron restriction strategy to reduce the pathogenicity of invasive microbes, while the other involves locally elevating iron levels to induce oxidative stress, thereby suppressing the pathogens. Correspondingly, pathogenic microorganisms have evolved diverse virulence strategies to counteract plant iron-related immunity. Through this review, we aim to provide insights for a deeper understanding of plant iron-signaling immune pathways and the functions and roles of iron in plant–pathogen interactions.