A variety of delivery vehicles have been explored as adjuvanting/delivery platforms for peptide-based subunit vaccines. Polysaccharide-based systems have been found to be especially attractive due to their immune stimulating properties, biodegradability, biocompatibility, and low toxicity. Among them, chitosan and its derivatives are the most common cationic nanocarriers used for the delivery of antigens. Trimethyl chitosan (TMC) is a partially quaternized, water-soluble, and mucoadhesive derivative of chitosan. This chapter describes the preparation of a TMC-based polyelectrolyte complex as a delivery system for peptide subunit vaccines.