Triple-negative breast cancer (TNBC) is a subtype of aggressive breast cancer with high recurrence and poor survival. Emerging evidence has indicated that long non-coding RNAs (lncRNAs) play pivotal roles in the development and progression of multiple cancers. Although there are substantial studies revealing that lung cancer-associated transcript 1 (LUCAT1) functions as a tumor promotor in various human cancers, the molecular mechanism of LUCAT1 in TNBC remains largely to be explored. In our study, we identified that LUCAT1 expression was dramatically enhanced in TNBC samples and cells. High LUCAT1 expression was strongly associated with advanced stages and poor prognosis of TNBC. LUCAT1 contributed to TNBC development through accelerating cell proliferation, cell cycle progression and metastasis as well as attenuating cell apoptosis. Moreover, miR-5702 was proved to directly bind to LUCAT1 and be negatively modulated by LUCAT1. Knockdown of miR-5702 reversed the suppressing influences of LUCAT1 depletion on TNBC progression. In conclusion, it was the first investigation to shed light on the significant function and underlying regulatory mechanism of LUCAT1 in TNBC tumorigenesis. We validated that LUCAT1 induced tumorigenesis and metastasis of TNBC via miR-5702, which provided clues for improving the treatment of TNBC.