Microtubules are highly dynamic structures, and their dynamic instability is indispensable for not only cell growth and movement, but also stress responses, such as endoplasmic reticulum (ER) stress. Docetaxel, a microtubule targeting agent (MTA), is the first-line drug for cancer treatment by simultaneously promoting microtubule dysregulation- and ER stress-induced cell death. However, it also causes adverse effects and drug resistance, especially in triple-negative breast cancer (TNBC) with a poor prognosis and high mortality rate. In this study, we developed a peptide-templated gold nanocluster, namely GA. GA significantly sensitizes TNBC cells to docetaxel, causing severe cell death. This effect is further validated by a 3D tumor spheroid model. Mechanistically, GA disrupted microtubule dynamic instability, meanwhile promoting PERK-mediated ER stress. Interestingly, ER stress inhibitors profoundly suppressed microtubule dysregulation, suggesting a retrograde regulation of ER stress on microtubules. In vivo, the combined administration of docetaxel and GA significantly suppresses tumor growth while docetaxel alone cannot. GA similarly elevated the level of caspases and PERK within tumors as in vitro. Importantly, GA treatment also profoundly promoted the production of anti-tumor inflammatory cytokines. Collectively, we developed an ER-microtubule regulatory nanomaterial that enhanced the therapeutic effect of docetaxel by elevating tumor cell death and anti-tumor cytokine production, providing a potential supplemental strategy for TNBC treatment.