Phytophthora capsici, a destructive fungal pathogen, poses a severe threat to pepper (Capsicum annuum L.) crops worldwide, causing blights that can result in substantial yield losses. Traditional control methods often come with environmental concerns or entail substantial time investments. In this research, we investigate an alternative approach involving ferrous sulfate (FeSO₄) application to combat P. capsici and promote pepper growth. We found that FeSO₄ effectively inhibits the growth of P. capsici in a dose-dependent manner, disrupting mycelial development and diminishing pathogenicity. Importantly, FeSO₄ treatment enhances the biomass and resistance of pepper plants, mitigating P. capsici-induced damage. Microbiome analysis demonstrates that FeSO₄ significantly influences soil microbial communities, particularly fungi, within the pepper root. Metabolomics data reveal extensive alterations in the redox metabolic processes of P. capsici under FeSO₄ treatment, leading to compromised cell membrane permeability and oxidative stress in the pathogen. Our study presents FeSO₄ as a promising and cost-effective solution for controlling P. capsici in pepper cultivation while simultaneously promoting plant growth. These findings contribute to a deeper understanding of the intricate interactions between iron, pathogen control, and plant health, offering a potential tool for sustainable pepper production.