Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype, accounting for 10-15% of all breast cancer cases. There are neither universally accepted prognostic markers, nor molecular targets related to TNBC. Therefore, the identification of biomarkers for personalized therapies is an unmet medical need. We have previously characterized the histamine H3 (H3R) and H4 (H4R) receptors in TNBC experimental models, demonstrating critical roles in tumor progression. In this study, we aimed to evaluate the expression of H3R and H4R in TNBC samples and the association with clinicopathological parameters. Fifty female patients with TNBC that underwent breast surgery at the British Hospital of Buenos Aires, Argentina, were retrospectively studied using archived paraffin-embedded tumor tissue specimens. Immunohistochemical analysis showed a higher H3R expression in neoplastic cells in comparison to normal ducts of the histopathologically normal peritumoral breast tissue (Mann Whitney test, P = 0.0177). A high level of H3R was associated with poor overall survival (OS) in TNBC patients (Gehan-Breslow-Wilcoxon test: χ2=4.162, P = 0.0413). Conversely, a low H4R expression was observed in aggressive tumors while its high expression correlated with improved overall and relapse-free survival (RFS) (RFS: P = 0.016; OS: P = 0.019). In addition, both receptors were expressed in murine 4T1 and human MDA-MB-231 TNBC cell lines, and treatment with H4R agonists or H3R antagonists demonstrated significant antiproliferative and pro-apoptotic effects. We conclude that both receptors might represent promising prognostic biomarkers in TNBC associated with tumor aggressiveness and patient survival. Targeting these receptors alone or in combination with current therapies may enhance TNBC treatment strategies.