This study aimed to investigate the effects of CpG oligodeoxynucleotide (CpG-ODNs)-coated chitosan nanoparticles (CNP) on the phenotype of murine macrophages and their proinflammatory cytokine profile in vitro. CNP-CpG-ODNs loaded with FITC-scrambled siRNA were prepared using the ionotropic gelation method. Peritoneal macrophages were isolated and exposed to CNP-CpG-ODNs. Treated macrophages were assessed for uptake capacity. Flow cytometry was used to evaluate the expression levels of MHC-II, CD40, and CD86 costimulatory molecules in treated macrophages. Furthermore, the secretion levels of proinflammatory cytokines (TNF-α and IL-6) and the release of nitric oxide (NO) were measured in the culture supernatant of treated macrophages using sandwich ELISA and the Griess reaction, respectively. These in vitro studies showed that CNP-CpG-ODNs had no cytotoxic effect on macrophages and were efficiently taken up by them. Additionally, CNP-CpG-ODNs significantly increased the production of TNF-α, IL-6, and NO in the culture supernatant compared to CNP alone. Moreover, CNP-CpG-ODNs enhanced the expression of MHC-II, CD40, and CD86 costimulatory molecules on macrophages. These findings indicate that incorporating CpG-ODNs into CNPs promotes macrophage maturation and a proinflammatory phenotype. Therefore, CNP-CpG-ODNs may serve as an effective system for targeted gene delivery to macrophages, enhancing immune responses.