CC chemokine ligand 21 (CCL21) is a known attractant for CCR7-positive (CCR7+) cells, but its additional role in the immunogenicity of CCR7+ cells remains poorly understood. This study explored the effects of CCL21-CCR7 ligation on cancer immunogenicity and related antitumor immune response, in the presence and absence of mitomycin C (MMC) treatment. CCL21-CCR7 binding upregulated human leukocyte antigen class I-restricted tumor antigen presentation with increased expression of human leukocyte antigen class I and transporter associated with antigen processing-1. In addition, CCL21 restrained the tumor-derived immunosuppressive factors FasL and transforming growth factor-β. Consequently, CCL21 facilitated cancer-educated lymphocytes reaction in vitro. In the tumor-bearing mouse, CCL21 inhibited tumor growth and prolonged mouse survival via lymphocytes, especially in CCR7+ cancer cells. Furthermore, Toll-like receptor 2 activation of lymphocytes assisted the tumor-suppression functions of CCL21, in vitro and in vivo. This study implies that CCL21 improved the immunogenicity of the CCR7+ breast cancer cell line even with MMC treatment and triggered antitumor response by lymphocytes. These findings provide a new insight into the research and application of CCL21-associated antitumor response.