<p>Biopolymers have emerged as sustainable and versatile alternatives to synthetic polymers due to their biodegradability, biocompatibility, and environmental friendliness. Among these, chitin has gained considerable attention for its broad spectrum of biological activities, particularly its antimicrobial potential. Chitin and its derivatives exhibit inherent antimicrobial properties attributed to their cationic nature and ability to disrupt microbial cell membranes. Over the years, extensive efforts have been made to enhance the antimicrobial efficacy of chitin-based materials through various modification strategies, including physical, chemical, and biological approaches, as well as through nanotechnology and the incorporation of antimicrobial agents. This review provides a comprehensive analysis of recent advancements (2020–2025) in the structural modification and functionalization of chitin-based materials aimed at improving their antimicrobial performance. The mechanisms underlying the antimicrobial action, structure–activity relationships, and synergistic interactions with incorporated agents are critically examined. Furthermore, the review explores the diverse applications of these enhanced materials in fields such as food packaging, wound healing, water treatment, and biomedical devices. By summarizing the current progress and identifying ongoing challenges, this work aims to guide future research directions in the design of effective chitin-based antimicrobial systems.</p>