Although microRNA-301a (miR-301a) has been reported to function as an oncogene in many human cancers, there are limited data regarding miR-301a and breast tumours. In this study, we first detected the expression of miR-301a using an in situ hybridization (ISH) -based classification system in 380 samples of BC tissue, including both non-TNBC (triple-negative breast cancer) and TNBC specimens. Our results suggest that analysing miR-301a expression in breast tissue biopsy specimens at the time of diagnosis could have the potential to identify patients who might be candidates for active surveillance. We validated our results that higher expression of miR-301a is associated with a decreased OS in independent public breast cancer databases, such as TCGA and METABRIC, using the online webtool Kaplan-Meier Plotter, which provided additional powerful evidence to confirm the prognostic value of miR-301a. MiR-301a may serve as a potential therapeutic target for patients with breast cancer. According to our results, miR-301a should be considered, and novel therapeutic options are needed to target this aggressive miR-301a-positive type of breast cancer to reduce recurrence and the mortality rate.