Background <p>Triple-negative breast cancer (TNBC) is a highly aggressive and heterogeneous breast cancer subtype with limited treatment options. Predicting patient response to chemo-immunotherapy remains challenging, highlighting the need for robust stratification strategies.</p> Methods <p>We performed a multi-parametric analysis combining histological, genomic, transcriptomic, proteomic, and immune profiling in the immunocompetent <i>MMTV-R26</i>^<i>Met</i> TNBC mouse model and compared outcomes with patient data from human TNBC cohorts and TNBC tumor microarray. To enable therapeutic testing and functional validation, we established syngeneic grafts from primary tumors and used them to evaluate combined chemotherapy (epirubicin) and anti-PD-1 immunotherapy.</p> Results <p>Multi-parametric analysis of TNBC heterogeneity modeled by the <i>MMTV-R26</i>^<i>Met</i> mice identified four distinct TNBC clusters, defined by unique intrinsic (molecular/genomic) and extrinsic (immune) features, which closely parallel patient subtypes, including rare metaplastic forms, and correlate with clinical outcomes. Both intrinsic and immune hallmarks of primary tumors were conserved across serial syngeneic transplantations, confirming the translational value of this preclinical platform. Treatment assessments indicated cluster-specific therapeutic vulnerabilities associated with molecular and immune traits. Specifically, whereas chemo-immunotherapy is beneficial to neutrophil-enriched tumors, immunotherapy alone appears to be more effective in macrophage-enriched tumors. Our findings indicate that TNBC treatment response is shaped by the interplay between tumor-intrinsic and immune features.</p> Conclusion <p>Our study provides a robust preclinical platform for precision immuno-oncology, enabling stratification of TNBC patients for tailored onco-immunotherapies.</p> Graphical Abstract <p></p>