HOTAIR plays an important role in the regulation of cancer cell proliferation and cancer invasion in breast cancer. The up-regulation of HOTAIR has been reported in both estrogen receptor (ER) positive and triple-negative (TN) breast cancer. It has been reported that HOTAIR is regulated by estrogen (E2) via ERs in ER-positive breast cancer. However, it is unknown how HOTAIR is regulated in TN breast cancer. In this study, we found that HOTAIR was increased in the peripheral blood mononuclear cells and cancer tissues from breast cancer patients, and was especially higher in patients with metastatic breast cancer. In addition, we found that estrogen promoted HOTAIR through its receptor GPER and estrogen-induced breast cancer cell migration was reversed by deleting HOTAIR in TN breast cancer cells MDA-MB-231and BT549. Furthermore, we identified that E2-GPER induces the level of HOTAIR through the suppression of miR-148a. miR-148a level was negatively correlated with HOTAIR level in breast cancer patients. After the mutation of the predicted miR-148a binding sites in HOTAIR, miR-148a had no effect on HOTAIR. In conclusion, our findings offer important new insights into the ability of estrogenic GPER signaling to increase the HOTAIR level by inhibiting miR-148a in breast cancer.