Breast cancer (BC) is most frequently recognized in women and characterized by histological and molecular heterogeneity. Among the various subtypes, triple-negative BC remains the most challenging disease owing to the lack of effective molecular targets and the high frequency of breast cancer stem cells (BCSCs), which account for both recurrence and resistance to conventional treatments. Despite the availability of hormonal therapies and targeted treatments, patients still face early and late relapses, necessitating new cytotoxic and selective treatment strategies. Our study focuses on investigating the effects of protocatechualdehyde (PCA), a potent bioactive compound derived from