Summary Nanotechnology is a fundamental technology for designing and generating innovative carriers for biomacromolecular drugs. Biodegradable poly(γ-glutamic acid)-based nanoparticles (γ-PGA NPs) are excellent vaccine carriers capable of delivering antigenic proteins to antigen-presenting cells (APCs) and eliciting potent immune responses based on antigen-specific cytotoxic T lymphocytes. In mice, subcutaneous immunization with γ-PGA NPs entrapping ovalbumin (OVA) more effectively inhibited the growth of OVA-transfected tumors than immunization with OVA emulsified using Freund's complete adjuvant. In addition, γ-PGA NPs did not induce histopathologic changes after subcutaneous injection or acute toxicity through intravenous injection. Importantly, γ-PGA NPs efficiently delivered entrapped antigenic proteins into APCs, and these antigen-capturing APCs migrated to regional lymph nodes. Our results demonstrate that a γ-PGA NP system for antigen delivery will advance the clinical utility of vaccines against cancer.