: Dendritic cell-based cancer immunotherapy is considered an innovative and promising approach aimed at enhancing the host's immune response to combat tumors. Additionally, IPI-549 has been identified as a first-line therapeutic option for breast cancer treatment. The objective of this research was to develop and formulate a novel therapeutic supplement by combining dendritic cells with IPI-549 (Eganelisib) for breast cancer treatment. The concurrent administration of dendritic cells and IPI-549 (DC-IPI) was utilized to treat mice and elicit immunological responses triggered by vaccination. Tumor regression and overall survival rates were evaluated across five distinct experimental groups. The administration of tumor cell lysate alongside DC-IPI resulted in a significant reduction in tumor growth and a two- to three-fold increase in the survival duration of treated mice. DC-IPI, whether decorated with mannan or not, elicited stronger responses in terms of delayed-type hypersensitivity, lymphocyte proliferation, and CD107a expression. Moreover, our findings demonstrated a reduction in IL-4 production in the supernatants of splenocyte cultures. A significant reduction in BRCA1 mRNA levels was also observed following treatment with DC-IPI. In conclusion, our results suggest that the DC-IPI antigen delivery system exhibited substantial anti-tumor efficacy in a breast cancer mouse model, representing a potential advancement in immunotherapy for human breast cancer.