Breast cancers are divided into at least 4 subtypes on the basis of gene expression profiles and expression of receptors (hormone receptors (HR) and HER2) as measured by immunohistochemistry. These subtypes have different prognoses and responses to treatments such as endocrine manipulation, anti-HER2 therapy, and chemotherapy. Triple-negative breast cancer (TNBC) is immunohistochemically defined as lacking estrogen and progesterone receptors and not overexpressing HER2. TNBC accounts for approximately 15% of breast cancer patients, and is more chemosensitive but has a worse prognosis than the HR-positive/HER2-negative phenotype. TNBC is a heterogeneous disease that does not offer specific targets in the same way as HR-positive and HER2-positive breast cancers, and is similar to basal-like breast cancer and BRCA1-related breast cancer. At present, the lack of highly effective therapeutic targets for TNBC leaves standard chemotherapy, for example the combination of anthracycline and taxane, as the only medical treatment, but this is insufficiently efficacious. Novel approaches for TNBC, for example DNA damaging agents, PARP-1 inhibitors, receptor tyrosin kinase inhibitors (TKIs), and antiangiogenesis agents, have been examined in clinical settings. Concerning therapeutic strategies for TNBC, it is most important to develop novel effective approaches for TNBC treatment and high-throughput predictive tools for standard chemotherapy and novel agents.