Breast cancer (BC) is a highly heterogeneous disease. While immunohistochemical analysis has been instrumental in classifying patients into distinct subgroups, there remains a need to refine the molecular classification of the disease. In this study, we focused on circulating regulatory RNA molecules (microRNAs, miRNAs) present as cell-free sources (cf-miRNAs) in plasma, exploring their potential as biomarkers to distinguish between different BC subtypes and their onset (early vs. late). Additionally, we investigated miRNAs secreted by cells into extracellular vesicles (vesicular miRNAs, EV-miRNAs). Utilizing a high-throughput hybridization protocol (nCounter, Nanostring), we examined the complete cf-miRNA and EV-miRNA profiles in pooled samples from BC patients, categorized into major subtypes: Luminal A (n=3), Luminal B (n=6), Luminal HER2 (n=6), HER2+ (n=3), and Triple-Negative (TNBC, n=12). Both cf-miRNA and EV-miRNA proved to be informative in discerning miRNA expression differences among BC subtypes. Notably, hsa-miR-197-3p was able to differentiate TNBC patients (cf-miRNA/EV-miRNA). Among the EV-miRNAs, hsa-miR-511-5p, hsa-miR-1206, hsa-miR-198, hsa-miR-33a-5p, hsa-miR-484, hsa-miR-627-3p, and hsa-miR-630 were indicative of early-onset TNBC patients and were proposed for validation in an independent cohort using the cost-effective technique of quantitative Reverse Transcription PCR (qRT-PCR). In an additional cohort of early-onset TNBC patients (n=20), we observed consistent expression of five out of seven markers tested using TaqMan probes. Interestingly, EV-miRNAs hsa-miR-627-3p, hsa-miR-511-5p, and hsa-miR-630 exhibited higher expression levels than the exogenous control (spike-in cel-miR-39-3p). As a future direction of this study, we aim to evaluate the potential of these pre-selected EV-miRNAs in i) monitoring patient status according to their treatments and ii) distinguishing early-onset TNBC patients from other non-triple-negative BC patients.