Abstract: Objective: To investigate the expression of CPEB2 in triple-negative breast cancer (TNBC) and its impact on the malignant progression of tumors. Methods: The expression level of CPEB2 in breast cancer was analyzed through database, and the differential expression in clinical pathological specimens was verified by immunohistochemical experiments. CPEB2 overexpressing stable TNBC cell lines were constructed, and CCK8 and Transwell assays were used to detect the changes in cell phenotypes. Western blot was used to explore the expression of key molecules in the MEK/ERK signaling pathway. Results: The expression of CPEB2 in TNBC tissues was significantly lower than that in adjacent tissues (χ² = 136.25, P < 0.001). Patients with high expression of CPEB2 had a significantly longer overall survival (OS) than those with low expression. Overexpression of CPEB2 inhibited the proliferation, migration and invasion abilities of TNBC cells and activated the MEK/ERK signaling pathway. Conclusion: The expression of CPEB2 is downregulated in TNBC, and its overexpression can activate the MEK/ERK signaling pathway to inhibit the proliferation, migration and invasion abilities of TNBC cells.