Chitosan is a natural, biocompatible, biodegradable, and non-toxic polymer that has consistently garnered the attention of researchers in the development of new materials across various applications. Typically, to impart the desired properties to chitosan, chemical modification is necessary. Therefore, the development of simple and convenient methods for the chemical modification of chitosan is crucial in polymer chemistry. In this work, the approaches of Click chemistry and the necessary electrochemistry, which have recently illuminated the chemistry of chitosan, were combined to achieve a straightforward and efficient synthesis of new tetrazole chitosan derivatives. This was accomplished through electrochemical coupling. The proposed synthesis method is simple, convenient, and fast, hence allowing for the easy production of low- (10%), moderate- (30%), and highly substituted (65%) tetrazole chitosan derivatives. The highly substituted chitosan derivatives exhibit high activity as catalysts for the aldol reaction, achieving almost 100% conversion in just 15 min. Notably, these derivatives enable the aldol reaction to be catalyzed in water, aligning with one of the key principles of green chemistry. Furthermore, the new tetrazole chitosan derivatives demonstrate significant in vivo antibacterial effects in the treatment of peritonitis in rats. The primary mechanism of their antibacterial action is the disruption of the bacterial cell membrane integrity. © 2025 Elsevier B.V., All rights reserved.