In vitro experiments with corresponding human triple negative BC cells (MDAMB‐231 and BT‐549) were used to verify the findings, we found that USP19 interacts with, deubiquitinates, and subsequently stabilises family molecular chaperone regulator 6 (BAG6) and BAG6 can boost B‐cell lymphoma‐2 (Bcl‐2) ubiquitination and degradation, thereby raising ER calcium (Ca2+) levels and causing ER stress. Here, USP19 is linked to breast cancer.