Owing to its inherent electrical conductivity, reversible redox activity, and structural versatility, polypyrrole (PPy) has become an important material for advanced functional coatings. This review summarizes recent advances in PPy-based coatings, systematically exploring the correlation between fundamental material design and macroscopic multifunctional applications. First, the core structural characteristics of PPy and its primary fabrication strategies, including electrochemical deposition, chemical oxidative polymerization, solution processing, and hybrid composite engineering, are delineated. Subsequently, the role of PPy in surface protection is analyzed, with an emphasis on the synergistic mechanisms underlying corrosion mitigation, mechanical durability, and environmental barriers (e.g., anti-fouling and solar-driven desalination). In addition, the application expansion of PPy in emerging fields, such as electromagnetic interference (EMI) shielding, highly sensitive smart sensing, electroactive energy interfaces, and advanced biomedical electrodes, is summarized. Finally, current challenges—particularly the physicochemical trade-offs among conductivity, interfacial adhesion, and long-term stability—are discussed, and future development directions are prospected. By integrating green processing technologies and data-driven smart system integration, next-generation PPy coatings are expected to meet the demands of flexible electronics, sustainable energy, and precision medicine.