Object: To identify the expression levels of ECT2 (epithelial cell transforming sequence 2) in triple-negative breast cancer (TNBC) before and after administration of paclitaxel (PTX) and explore the interaction between ECT2 and PTX in breast cancer treatment. Methods: Lentiviral (LV) packaging ECT2 overexpression and interference plasmids were constructed for in vitro assays. The effects of ECT2 expression on the TNBC cell line (HCC1806), particularly its roles in the proliferation, invasion, migration and apoptosis and cell cycle, were evaluated using the CCK-8 and other methods before and after PTX treatment. In nude mouse xenograft settings were performed to detect cell apoptosis and Ki-67 expression levels by TUNEL and immunohistochemical staining, respectively. Results: In the vitro assays, before and after the PTX treatment, comparison of the LV-ECT2 and sh-ECT2 groups and the remaining three groups (control, LV-NC, sh-NC) showed statistically significant differences in terms of cell proliferation, invasion and migration and apoptosis and changes in the cell cycle. In the vivo assays, the control, LV-ECT2 and shECT2 groups markedly outweighed the corresponding PTX-treated groups. The LV-ECT2, PTX, sh-ECT2 and sh-ECT2-PTX were all significantly different from the control group in terms of body weight and tumour size changes. Cell apoptosis occurred in the PTX, sh-ECT2 and sh-ECT2-PTX groups. About the Ki-67 proliferation index, the PTX, LV-ECT2-PTX, sh-ECT2 and sh-ECT2-PTX groups were significantly different from the control group. Conclusion: ECT2, which is a major driving factor in the growth of breast cancer cells, plays an important role in regulating TNBC growth. PTX therapy had significantly improved efficacy after silencing ECT2. This finding indicates that the inhibition of ECT2 expression may facilitate the treatment of breast cancer as a new regimen and provide a theoretical basis for the development of new targeted drugs as a replacement for PTX in breast cancer treatment.