Proteomics is an already established transformative tool for dissecting the molecular mechanisms underlying plant immunity and pathogen virulence. As crop losses due to plant diseases intensify under climate change, understanding these interactions at the protein level has become essential for sustainable crop improvement. Advances in mass spectrometry, bioinformatics, and quantitative proteomics have expanded the capacity to characterize dynamic changes in host and pathogen proteomes, enabling the identification of defense-related proteins, signaling networks, effector targets, and pathogenicity determinants. This chapter synthesizes recent proteomic insights across major crops as soybean, tomato, rice, grapevine, maize, and wheat, highlighting how proteome profiling has revealed key regulators of pathogen-associated molecular pattern (PAMP)-triggered and effector-triggered immunity, pathogen infection strategies, and the impact of biocontrol agents and priming compounds. Case studies illustrate how proteomics uncovers cultivar-specific responses, subcellular reprogramming, and protein networks critical for resistance. We further explore how proteomics informs biotechnology, from identifying candidate genes for breeding and genome editing to supporting safety assessments of engineered crops.