Triple-negative breast cancer (TNBC) is the most aggressive and malignant breast cancer. Ferroptosis is an oxidative, iron-dependent form of regulated cell death. Ferroptosis-targeted therapies is a promising approach to improving treatment outcomes of TNBC. Combining death pathway inhibitors with relevant indices for ferroptosis and LipROS, this study uncovered that a natural product of 4, 9-dihydroxy-α-lapachone (DLN) from Catalpa bungei "jinsi" exhibited in vitro and in vivo inhibitory activity against TNBC via ferroptosis. The molecular mechanism is an activation of the FTH1 led to iron overload, and then inhibition of cysteine-glutamate antiporter (system Xc-) and GPX4, which further sensitized TNBC cells to ferroptosis. This study clarified the pathway of DLN-induced cell death in TNBC treatment and exhibited its potential as therapeutic agent for TNBC.